What is the answer to 9/4 = r/(r-4) ?

The answer to 9/4 = r/(r-4) is r= 36/5

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9/4 = r/(r-4)

\frac{9}{4} = \frac{r}{r - 4}

r = \frac{36}{5}

Decimal Notation

r = 7.2

Solution steps

\frac{9}{4} = \frac{r}{r - 4}

Cross multiply

9 r - 36 = 4 r

Move

36

to the right side

9 r = 4 r + 36

Move

4 r

to the left side

5 r = 36

Divide both sides by

5

r = \frac{36}{5}

Verify Solutions

Find undefined (singularity) points:

r = 4

Combine undefined points with solutions:

r = \frac{36}{5}

\frac{23.8}{17} = \frac{53}{x}

\frac{2 x - 3}{x + 1} = 3

\frac{10}{x} = \frac{4}{8}

3 = \frac{8}{h}

\frac{1}{2} = \frac{2 π}{b}