А+(45-30)=75? х-(23+17)=60? (30-15)+у=80? х+12=50-(15+5)?

Решите задачу:

$a +( 45 - 30) = 70 \\ a + 45 - 30 = 70\\ a + 5 = 70 \\ a = 70 - 5 \\ a = 65$

$x - (27 + 17) = 60 \\ x - 27 - 17 = 60 \\ x - 10 = 60 \\ x = 60 + 10 \\ x = 70$

$(30 - 15) + y = 80 \\ 30 - 15 + y = 80 \\ 15 + y = 80 \\ y = 80 - 15 \\ y = 65$

$x + 12 = 50 - (15 + 5) \\ x + 12 = 50 - 15 - 5 \\ x + 12 = 30 \\ x = 30 - 12 \\ x = 18$