Question

12:(d×3)=21:3;(b:3)×6=52-4;60-(e×9)=30:5;9×(c:6)=6×6;72-40=(f:3)×(40:5)

Answer 1

12:(d×3)=21:3
12:3d=7
3d=12/7 |:3
d=12/21
d=4/7

(b:3)×6=52-4
(b:3)×6=48
b:3=48:6
b:3=8
b=8×3
b=24

60-(e×9)=30:5
60-9e=6
-9e=6-60
-9e=-54 |:(-9)
e=6

9×(c:6)=6×6
9×(c:6)=36
c:6=36:9
c:6=4
c=4×6
c=24

72-40=(f:3)×(40:5)
32=(f:3)×8
f:3=32:8
f:3=4
f=4×3
f=12