1) 54 - 16 : {[ 36-6×4 :(x -4×5)] :5 + 2} = 52.
16 : {[ 36 - 6×4 : (x - 4×5)] :5+2}=54-52
16 : {[ 36 - 6×4 : ( x-4×5)]:5+2}=2
[36-6×4 :(x-4×5)]:5+2=16:2
[36 - 6×4:(x-4×5)]:5+2=8
[36-6×4:(x-4×5)]:5=8-2
[36-6×4:(x-4×5)]:5=6
[36-6×4:(x-4×5)]=6×5
36-6×4:(x-4×5)=30
6×4:(x-4×5)=36-30
6×4:(x-4×5)=6
24:(x-20)=6
x-20=24:6
x-20=4
x=4+20
x=24.
2) 167-a + 3×90=415
167-a+270=415
167-a=415-270
167-a=142
a=167-142
a=25.
