a) (5 x a) - 24 = 26
5 x a = 26 + 24
5 x a = 50
a = 50 : 5
a = 10
b) 36 - (18 : a) = 30
-(18 : a) = 30 - 36
-(18 : a) = -6
18 : a = 6
a = 18 : 6
a = 3
c) 45 + (5 x a) = 50
5 x a = 50 - 45
5 x a = 5
a = 5 : 5
a = 1
1. I = 16 : 2
I = 8
C = 21 : 3
C = 7
D : I = C
D = C x I
D = 7 x 8
D = 56