Question

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

Answer 1

u = 30

continuing your method

`(1)/(10)` =
`(1)/(u)` +
`(1)/(15)`

subtract
`(1)/(15)` from both sides

`(1)/(u)` =
`(1)/(10)` -
`(1)/(15)` thus

`(1)/(u)` =
`(3)/(30)` -
`(2)/(30)`

`(1)/(u)` =
`(1)/(30)` ⇒ u = 30

Answer 2

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