\(\frac{a+12}{b+18}=\frac{a}{b}=\frac{a+12-a}{b+18-b}=\frac{12}{18}=\frac{2}{3}\)
vậy \(\frac{a}{b}=\frac{2}{3}\)
Theo bài ra ta có :
\(\frac{a+12}{b+18}=\frac{a}{b}\)hay \(\frac{\left(a+12\right).b}{\left(b+18.b\right)}=\frac{a.\left(b+18\right)}{b.\left(b+18\right)}\)(quy đồng mẫu số )
Vậy ta được : ( a + 12 ) x b = a x ( b + 18 )
a x b + 12 x b = a x b + a x 18
12 x b = a x 18
\(\frac{12.b}{18.b}=\frac{a.18}{18.b}\)
\(\frac{12}{18}=\frac{a}{b}\)
Vậy \(\frac{a}{b}=\frac{12}{18}=\frac{2}{3}\)