Помогите решить уравнение (5y-7)*(4y-0,8)=0 (3,7x-1,24)*2,5=8 (5,4y+8,3)*2,1=23,1...

1)
$(5y - 7)(4y - 0.8) = 0 \\$
$5y - 7 = 0 \\ 5y = 7 \\ y = \frac{7}{5} = 1 \frac{2}{5}$
или
$4y - 0.8 = 0 \\ 4y = 0.8 \\ y = \frac{0.8}{4} = 0.2$
Ответ: 0,2; 1 2/5.

2)
$(3.7x - 1.24) \times 2.5 = 8 \\ 3.7x - 1.24 = \frac{8}{2.5} \\ 3.7x - 1.24 = 3.2 \\ 3.7x = 1.24 + 3.2 \\ 3.7x = 4.44 \\ x = \frac{4.44}{3.7} = \frac{444}{100} \div \frac{37}{10} = \frac{444}{100} \times \frac{10}{37} = \frac{12}{10} = 1.2$
Ответ: 1,2.

3)
$(5.4y + 8.3) \times 2.1 = 23.1 \\ 5.4y + 8.3 = \frac{23.1}{2.1} = \frac{231}{10} \div \frac{21}{10} = \frac{231}{10} \times \frac{10}{21} = 11 \\ 5.4 y+ 8.3 = 11 \\ 5.4 y= 11 - 8.3 = 2.7\\ y = \frac{2.7}{5.4} = \frac{1}{2} = 0.5$
Ответ: 0,5.

4)
$(4.2y - 3.96) \times 1.5 = 8.55 \\ 4.2y - 3.96 = \frac{8.55}{1.5} = \frac{855}{100} \div \frac{15}{10} = \frac{855}{100} \times \frac{10}{15} \frac{57}{10} = 5.7 \\ 4.2y - 3.96 = 5.7 \\ 4.2y = 5.7 + 3.96 = 9.66 \\ y = \frac{9.66}{4.2} = \frac{966}{100} \times \frac{10}{42} = \frac{23}{10} = 2.3$
Ответ: 2.3