-2, 4m*(-3)
a-(a+5) +(-7+a)
-8a-12b+5a+17b
-5(y-4) +(y+5)

-2,4m · ( -3 ) = 7,2m

a - ( a + 5 ) + ( -7 + a ) = a - a - 5 - 7 + a = -12 + a

-8a - 12b + 5a + 17b = -8a + 5a - 12b + 17b = -3a + 5b

-5 ( y - 4 ) + ( y + 5 ) = -5 · y - 5 · ( -4 ) + y + 5 = -5y + 20 + y + 5 = -4y + 25