Question

8*x+7*x=90 помогите пожалуйста

Answer 1

$8x + 7x = 90 \\ 15x = 90 \\ x = 90 \div 15 \\ x = 6 \\ - - - - - - - \\ 8 \times 6 + 7 \times 6 = 90 \\48 + 42 = 90 \\ 90 = 90$