Răspuns:
Ex. 2
a) x + 14 = 18 => x = 18 - 14 => a = 4
b) 142 + x = 420 => x = 420 - 142 => x = 278
c) x - 140 = 320 => x = 320 + 140 => x = 460
d) 51 - x = 18 => x = 51 - 18 => x = 33
e) 2x = 14 => x = 14 : 2 => x = 7
f) x * 7 = 420 => x = 420 : 7 => x = 60
g) x : 15 = 9 => x = 9 * 15 => x = 135
h) 231 : x = 3 => x = 231 : 3 => x = 77
i) x * x = 4 * 4 => x = 4
j) [tex]5^{x}[/tex] = [tex]5^{7}[/tex] => x = 7
Ex. 3
a) 2x + 15 = 37 => 2x = 37 - 15 => 2x = 22 = > x = 22 : 2 => x = 11
b) 14 + 5x = 24 => 5x = 24 - 14 => 5x = 10 => x = 10 : 5 => x = 2
c) ( 53 - 3 + x ) - 48 = 24 => 53 - 3 + x = 24 + 48 => 53 - 3 + x = 72 =>
=> 53 + x = 72 + 3 => 53 + x = 75 => x = 75 - 53 => x = 22
d) 50 + 70 - ( 36 - x ) = 100 => 70 - ( 36 - x ) = 100 - 50 => 70 - ( 36 - x ) = 50
=> - 36 + x = 50 - 70 => x = 36 - 20 => x = 16
e) 2( x + 4 ) = 76 => x + 4 = 76 : 2 => x + 4 = 38 = > x = 38 - 4 => x = 34
f) 5( x + 1 ) = 105 - 75 => 5( x + 1 ) = 30 => x + 1 = 30 : 5 => x + 1 = 6 =>
x = 6 - 1 => x = 5
Ex. 4
a) 2x = x + 8 => 2x - x = 8 => x = 8
b) 5x - 4 = 2x + 20 => 5x - 2x = 4 + 20 => 3x = 24 => x = 24 : 3 => x = 8
c) 2( x - 1 ) = 4 + x => 2x - 2 = 4 + x => 2x - x = 4 + 2 => x = 6
d) 4x + 17 = 3( x + 20 ) => 4x + 17 = 3x + 60 => 4x - 3x = 60 - 17 =>
x = 43
