A's marks in Biology are 20 less than 25% of the total marks obtained by him in Biology, Maths and Drawing… · ABC26GN2365

Let $\mathrm{B}+\mathrm{M}+\mathrm{D}=x$. Then, $\mathrm{B}=25 \%$ of $x-20$ $$\begin{aligned} & =\left(\frac{25}{100} x-20\right)=\left(\frac{x}{4}-20\right) \text { and } \mathrm{D}=50 . \\ & \therefore \frac{x}{4}-20+\mathrm{M}+50=x \text { or } \mathrm{M}=\left(\frac{3 x}{4}-30\right) . \end{aligned}$$ So, marks in Maths cannot be determined.