Question

63-49+a=71 si 91-36-a=27 a-(18-9)=16

Answer 1

14 + a = 71
a = 71-14
a=57

55 - a = 27
a= 55-27
a=28

a- 9 = 16
a= 16 + 9 
a= 25

Answer 2

63-49+a=71<=>14+a=71=>a=71-14=57; 91-36-a=27<=>55-a=27<=>55-27=a=>a=28; a-(18-9)=16<=>a-9=16=>a=16+9=25.