54 : y + 81 : y = 3
54 : 1/y + 81 : 1/y = 3
1/y x ( 54 + 81 ) = 3
1/y x 135 = 3
1/y = 3 : 135
1/y = 1/45
=> y = 45
Vậy y = 45
Tk mk nha đúng đó !!
54 : y + 81 : y = 3
(54+81):y=3
135:y=3
y=135 : 3
y=45
Ta có :
\(\frac{54}{y}+\frac{81}{y}=3\)
\(\Rightarrow\frac{54+81}{y}=3\)
\(\Rightarrow\frac{135}{y}=3\)
\(\Rightarrow y=135\div3=45\)
Vậy y = 45
\(54\div y+81\div y=3\)
\(54\times\frac{1}{y}+81\times\frac{1}{y}=3\)
\(\left(54+81\right)\times\frac{1}{y}=3\)
\(135\times\frac{1}{y}=3\)
\(\frac{1}{y}=3\div135\)
\(\frac{1}{y}=\frac{1}{45}\)
Vậy \(y=45.\)
