The article:

Here are more equations with one unknown.

With addition:

64 + x = 87
X = 87 - 64
X = 23

Y + 4 + 23 = 56
Y + 27 = 56
Y = 56 - 27
Y = 29

With subtraction:

47 - x = 44
X = 47 - 44
X = 3

X - 28 = 78
X = 78 + 28
X = 106

With multiplication

20x = 80
X = 80 : 20
X = 4

8y = 136
Y = 136 : 8
Y = 17

With division:

45 : x = 9
X = 45 : 9
X = 5

Y : 7 = 8
Y = 8 x 7
Y = 56

More exercises:

Here are more equations if you want to test yourself with some exercises:

X + 76 = 152

154 - y = 48

A : 9 = 26

B x 6 = 66

70 : c = 10