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we're asked to evaluate the expression a squared plus 10 B minus 8 when a is equal to 7 and B is equal to 4 so to evaluate the expression we really just have to substitute a with 7 and substitute B with negative 4 because they're saying evaluate it when a is equal to 7 and B is equal to negative 4 so let's do that so a everywhere where we see an A in the expression we should put a 7 there so instead of a squared instead of a squared we should write 7 squared + + I'll do it in that same color plus 10 times B but instead of a instead of a B there we are now going to substitute it with B is equal to negative 4 so 10 times 10 times negative 4 instead of the instead of the B right over there and then we have the minus 8 and now we just have to evaluate this thing 7 squared is 49 49 and then 10 times negative 4 remember order of operations multiplication comes before addition so we have to multiply this 10 times negative 4 is negative 40 so it's plus plus negative 40 and then we have minus 8 minus 8 back over here and so we get 49 plus negative 40 which is really the same thing as 49 minus 40 is going to be 9 and then we're going to subtract 8 from that and so we get 149 minus 40 is 9 minus 8 is 1 and we are done we've evaluated the expression when a is equal to 7 and B is equal to negative 4