Question

rez (36+2*a):6+12=110-89

Answer 1

$(36+2a):6+12=21\\ (36+2a):6=21-12\\ (36+2a):6=9\\ (36+2a)=9*6\\ (36+2a=54\\ 2a=66-54\\ 2a=18\\ a=18:2\\ a=9.$

Answer 2

(36+2*a):6+12=21
(36+2*a):6=21-12
(36+2*a):6=9
(36+2*a)=9*6
36+2*a=54
2*a=54-36
2*a=18
a=18:2
a=9