Question

a + 3b = 42
2a + 4b = 64​

Answer 1

Explicación paso a paso:

$1. \: \: \: \: \: \: \: a = 42 - 3b \\ 2. \: \: \: \: \: \: 2a = 64 - 4b \\ a = \frac{64 - 4b}{2}$

$\frac{64 - 4b}{2} = 42 - 3b \\ 64 - 4b = 84 - 6b \\ - 84 + 64 = - 6b + 4b \\ - 20 = - 2b \\ 2b = 20 \\ b = \frac{20}{2} = 10$

$a + 3b = 42 \\ a + 3 \times 10 = 42 \\ a + 30 = 42 \\ a = 42 - 30 \\ a = 12$

$2 \times 12 + 4 \times 10 = 64 \\ 12 + 3 \times 10 = 42$

espero te sirva