1

Solve

\$ \sqrt{\frac{5x + 1}{4x - 1}} = 3 \$

2

Apply square on both sides

\$ (\sqrt{\frac{5x + 1}{4x - 1}})^2 = (3)^2 \$

3

After canceling square and squareroot

\$ {\frac{5x + 1}{4x - 1}} = 9 \$

4

Move \$ {4x - 1} \$ to right side

\$ 5x + 1 = 9(4x - 1) = 36x - 9 \$

5

Move variables to left side

\$ 5x - 36x = -9 - 1 \$

6

After simplification

\$ -31x = -10 \$

7

Dividing on both sides by '\$-31\$' of the equality

\$ \cancel(-31)/\cancel(-31)x = \cancel(-) 10/\cancel(-)(31) \$

8

After cancelation

\$ x = 10/31 \$

9

Answer

C = \$ x = 10/31 \$