If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:3:04

Video transcript

we have the equation negative is 16 is equal to x over 4 plus 2 and we need to solve for X so really just need to isolate the X variable on one side of this equation and the best way to do that is first to isolate it isolate this whole X / 4 term from all of the other terms so in order to do that let's get rid of this - and the best way to get rid of that - is to subtract it but if we want to subtract it from the right-hand side we also have to subtract it from the left-hand side because this is an equation if this is equal to that anything we do to that we also have to do to this so let's subtract 2 from both sides so you subtract 2 from the right subtract 2 from the left and we get on the left-hand side negative 16 minus 2 is negative 18 and then that is equal to X / 4x over 4 and then we have positive 2 minus 2 which is just going to be 0 so we don't even have to write that I could write just a plus 0 but I think that's a little unnecessary and so we have negative 18 is equal to x over 4 and our whole goal here is to isolate the X to solve for the X and the best way we could do that if we have x over 4 here if we multiply that by 4 we're just going to have an X so we can multiply that by 4 but once again this is an equation anything you do the right-hand side you have to do to the left-hand side and vice versa so if we multiply the right-hand side by 4 we also have to multiply the left-hand side by 4 so we get 4 times negative 18 is equal to x over 4 times 4 the x over 4 times 4 that cancels out you divide something by 4 and multiply by 4 you're just going to be left with an X and on the other side 4 times negative 18 let's see that's 40 well let's just write it out so 18 times 4 if we were to multiply 18 times 4 4 times 8 is 32 4 times 1 is 4 plus 1 is 72 but this is negative 18 times 4 so it's negative 72 so X is equal to negative 72 and if we want to check it we can just substitute it back into that original equation so let's do that let's substitute let's substitute this into the original equation so the original equation was negative 16 is equal to instead of writing X I'm going to write negative 72 is equal to negative 72 over 4 over 4 plus 2 let's see if this is actually true so this right-hand side simplifies to negative 72 divided by 4 we already know that that is negative 18 so this is equal to negative 18 plus 2 this is what the equation becomes and then the right-hand side negative 18 plus 2 that's negative 16 so it all comes out through this right-hand side when X is equal to negative 72 does indeed equal negative 16