Đáp án:
x. $\frac{1}{4}$ + x.$\frac{1}{5}$ + x.2 = = 19,2
x. ($\frac{1}{4}$ + $\frac{1}{5}$ + 2) = $\frac{96}{5}$
x. ($\frac{5}{20}$ + $\frac{4}{20}$ + $\frac{40}{20}$) = $\frac{96}{5}$
x. $\frac{49}{20}$ = $\frac{96}{5}$
x = $\frac{96}{5}$ : $\frac{49}{20}$
x = $\frac{384}{49}$