Calculating Marks

If you’re test was such that you scored $\frac{50}{75}$ for a test that represents $\frac{3}{4}$ of your entire mark you would calcuate it by taking 3 quarters of 50 and then dividing by 75:

$\begin{aligned} \text{Marks} &= \frac{3}{4} \times \frac{50}{75} \\ &= 0.75 \times 0.67^.\\ \implies &= 50\% \end{aligned}$

$\therefore$ your overall marks for the unit garnered by this test was 50%

Code

sympy 50/75 
sympy 3/4*50/75

> 0.66
> 0.5