The same way you do positive numbers, you do negative number. Multiply whatever is in the parenthesis by what's on the outside, which in this case is -10. So:
-10*s + -10*1 = -87 -10s + -10 = -87
To solve, first add -10 to both sides
-10s = -77
next, divide both sides by -10
s = 7.7
To check the answer, plug the solution into the original equation -10(s+1) = -87 -10(7.7 + 1) = -87 -10(8.7) = -87 -87 = -87
(for the first one, is there a variable involved?)
