Express and operate with time in hours, minutes and seconds

Since the minutes to subtract $(35)$ are bigger than those that we have $(3)$ we must subtract one hour from the original time and add $60$ minutes to the minutes of this first time. This leads us to the operation to be calculated as:

$$(4h \ 63 ' \ 34 '' )-(1h \ 35 ' \ 21 '' )$$

Once we have the expressed the operation like this, we proceed to subtract each of the factors separately and we have:

$$3h \ 28 ' \ 13 ''$$

We multiply every factor by $5$ and we get: $30h \ 35' \ 275''$

Since we have more than $60$ seconds, we convert them into minutes. We divide $275$ by $60$. We take the integer part.

$$\dfrac{275}{60}=4,5833$$

We multiply the integer part $4$ by $60$ and we subtract it from $275$ original. We get:

$$4 \cdot 60 = 240 \Rightarrow 275-240=35$$

Therefore, we must add $4$ more minutes to the result and leave only $35$ seconds. This is: $30h \ 39' \ 35'' $