Question

a+(a-10)-(12+a)
16+3(2-3y)+8y
15-5(1-a)-6a

Answer 1

$1) \: \: a + (a - 10) - (12 + a) = a + a - 10 - 12 - a = \\ = a - 22$
$2) \: 16 + 3(2 - 3y) + 8y = 16 + 6 - 9y + 8y = \\ = 22 - y$

$3) \: \: 15 - 5(1 - a) - 6a = 15 - 5 + 5a - 6a = \\ = 10 - a$