Question

31-(a+x)=17
x=16
a=? ​

Answer 1

31-(a+x)=17

x=16

31-(a+16)=17

31-а-16=17

-а=17-31+16

-а=2

а=-2

Answer 2

$31 - (a + 16) = 17 \\ 31 - a - 16 = 17 \\ 15 - a = 17 \\ - a = 17 - 15 \\ - a = 2 \\ a = - 2$