câu a x =2/3
câu b x=-90
a, x-1/4=5/8 . 2/3
\(x-\frac{1}{4}=\frac{5}{12}\)
x = \(\frac{5}{12}+\frac{1}{4}\)
x = \(\frac{2}{3}\)
b, x/126= -5/4 .4/7
\(\frac{x}{126}=\frac{-5}{7}\)
=> x .7 = (-5) . 126
=> x . 7 = -630
=> x = (-630) :7
=> x = -90
Học tốt
\(x-\frac{1}{4}=\frac{5}{8}.\frac{2}{3}\)
\(x-\frac{1}{4}=\frac{5}{12}\)
\(x=\frac{5}{12}+\frac{1}{4}\)
\(x=\frac{2}{3}\)
\(\frac{x}{126}=\frac{-5}{4}.\frac{4}{7}\)
\(\frac{x}{126}=\frac{-5}{7}\)
\(\Rightarrow7x=-630\)
\(x=-630:7\)
\(x=-90\)