Answer
option b
Work Step by Step
Step 1: $\frac{3}{7x}+\frac{5}{7}$
Step 2: $\frac{3\times1}{7x \times 1}+\frac{5\times x}{7 \times x}$
Step 3: $\frac{3}{7x}+\frac{5x}{7x}$
Step 4: $\frac{3+5x}{7x}$
Step 5: Therefore the answer is option b