a) 70-5 ( x - 3 )= 45
5 ( x - 3 ) = 70 - 45
5 ( x - 3 ) = 25
x - 3 = 25 : 5
x - 3 = 5
x = 5 + 3
x = 8
b) 10 + 2.x = $4^{5}$ : $4^{3}$
10 + 2.x = $4^{2}$
10 + 2.x = 16
2.x = 16 - 10
2.x = 6
x = 6 : 2
x = 3
c) [ ( 4.x +28 ) .3 +55 ] : 5 = 35
( 4.x +28 ) .3 +55 = 35 . 5
( 4.x +28 ) .3 +55 = 175
( 4.x + 28 ) . 3 = 175 - 55
( 4.x + 28 ) . 3 = 120
4.x + 28 = 120 : 3
4.x + 28 = 40
4.x = 40 - 28
4.x = 12
x = 12 : 4
x = 3
d) ( 2x - 2 ) $^{2}$ - 4 = 21
( 2x - 2 ) $^{2}$ = 21 + 4
( 2x - 2 ) $^{2}$ = 25
( 2x - 2 ) $^{2}$ = $5^{2}$
⇒ 2x - 2 = 5
⇒ 2x = 5 + 2
⇒ 2x = 7
⇒ x = 7 : 2
⇒ x = 3, 5
e) $3^{2x + 1}$ + $3^{2x}$ = 324
$3^{2x}$ + $3^{2x}$ . 3 = 324
$3^{2x}$ . ( 1 + 3 ) = 324
$3^{2x}$ . 4 = 324
$3^{2x}$ = 324 : 4
$3^{2x}$ = 81
$3^{2x}$ =$3^{4}$
⇒ 2x = 4
⇒ x = 4 : 2
⇒ x = 2
