1. a) 6^2 : 4 +2 .5^2= 36 : 4 + 2 . 25 = 9+50=59
b) 2(5.4^2 -18) = 2( 5.16-18) = 2 (80-18) = 2. 62 = 132
2. a) (6x-39):3 = 201
=> 6x - 39 = 201 . 3 = 603
=> 6x = 603+39 = 642
=> x = 642 : 6 = 107
b) 23+3x = 5^6:5^3
23+3x = 125
3x = 125-23 =102
x = 102 : 3 = 34