Question 212380
(-12) - (7 - (-6)) - (7 - (-15) - (-10))
= (-12) - (7 + 6) - (7 + 15 + 10) ................. note that a-(-b)=a+b
= (-12) - 13 - 32
= -12 - 13 - 32   .........................note that (-a) = -a
= -57