Tìm x: a) 2x + 7 = 15

e) H = {x ∈ Z | -3 < x ≤ 3}

H = {-2; -1; 0; 1; 2; 3}

a) 2x + 7 = 15

2x = 8

x = 4

b) 25 - 3.(6 - x) = 22

3.(6 - x) = 3

6 - x = 1

x = 5

c) (7x - 15) : 3 = 9

7x - 15 = 9

7x = 24

x = 24/7

d) 71 + (x - 16 : 2²) = 75

x - 16 : 4 = 4

x - 4 = 4

x = 8