Respuesta :

sqdancefan

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

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