Setting up a system of equations from context example (pet weights)

in this video we're going to get some more practice setting up systems of equations not solving them but just setting them up so we're told sunjai's dog weighs five times as much as his cat his dog is also 20 kilograms heavier than his cat let's see B the cats weight and let D be the dog's weight so pause this video and see if you can set up a system of equation two linear equations with two unknowns that we could use to solve for C and D but we don't have to in this video all right so let's do it together so what I like to do is usually there's a sentence or two that describes each of the equations we want to set up so this first one tells us sunjai's dog weighs five times as much as his cat so how much does his dog way so his dog weighs d so we know D is going to be equal to five times as much as his cat weighs so his cat weighs C so D is going to be equal to five times as much as his cat weighs so that's one linear equation using D and Z and so what's another one well then we are told his dog is also 20 kilograms heavier than his cat so we could say that the dog is going to be equate is going to be equal to the cats weight Plus what plus 20 kilograms we're assuming everything's in kilograms so I don't have to write the unit's but there you have it I have just set up two equations in two unknowns two linear equations based on the information given in this word problem which we could then solve and I encourage you to do so if you're so if you're curious but sometimes the difficult part is just to find is to reexpress the information that you're given in a mathematical form but as you see you as you get practice it becomes somewhat intuitive that what we see in blue is just another way of writing what we underlined in blue and what we see in yellow is just another way of writing or expressing what we underlined in yellow up there