Question

vreau urgent
dau coroana :)

Answer 1

$a = 2 \times b \\ \\ m = \frac{a \times 3 + b \times 7}{3 + 7} = 3.9 \\ \\ \frac{2 \times b \times 3 + b \times 7}{10} = 3.9 \\ \\ 6 \times b + 7 \times b = 39 \\ \\ 13 \times b = 39 \\ \\ b = 39 \div 13 = 3$
a=2×b=2×3=6