Question

When Tom found found the difference -11 - (-4) he got an answer of -15. What might Tom have done wrong?

Answer 1

Tom apparently added -4 to -11 instead of subtracting it.

Answer 2

Tom combined like terms as if it were an equation instead of solving the problem. -11-(-4) would turn into a -11+4 and to solve that do 11-4=7 but the 7 is negative because the bigger number in that problem (11) was negative. -11-(-4)=-7