Question

711-3x[42-2x(2a+3b)]=639

Answer 1

711-3x[42-2x(2a+3b)]=639

3x[42-2x(2a+3b)] = 711 - 639

3x[42-2x(2a+3b)] = 72

42 - 2×(2a+3b) = 72 : 3

42 - 2 × (2a+3b) = 24

2 × (2a+3b) = 42 - 24

2 × (2a + 3b) = 18

2a + 3b = 18 : 2

2a + 3b = 9

pentru a = 3
6 + 3b = 9
3b = 9 - 6
3b = 3
b = 1

a = 3
b = 1

Answer 2

711 - 3 (-2 x 2a - 2 x 3b + 42) = 639
711 - 3 (-4a - 6b + 42) = 639
711 + 3 x 4a + 3 x 6b - 126 = 639
711 + 3 x 4a + 3 x 6b - 126 - 639 = 639 - 639
6(2a + 3b - 9) = 0
= 3b + 9 / 2.