Question

I'm appreciate if anyone can help me to do this question .. Question 5.. Thank you.

Answer 1

The value of u is 5. 1/10 = 1/5 + 1/15 = 2/20 which equals 1/10

Answer 2

u = 30

continuing your method

$\frac{1}{10}$ = $\frac{1}{u}$ + $\frac{1}{15}$

subtract $\frac{1}{15}$ from both sides

$\frac{1}{u}$ = $\frac{1}{10}$ - $\frac{1}{15}$ thus

$\frac{1}{u}$ = $\frac{3}{30}$ - $\frac{2}{30}$

$\frac{1}{u}$ = $\frac{1}{30}$ ⇒ u = 30