Ananya has Rs. 350 in denomination of Rs. 50, Rs. 5 and Rs. 20. If the number of Rs. 20 notes is same as the number of Rs. 5 notes. The total number of notes is Rs. 10, then the number of Rs. 50 notes is

Total number of notes = 10 

No. of Rs. 20 notes =  No. of Rs. 5 notes = 𝑥 

No. of Rs. 50 notes = 𝑦 

So by the problem

$x+x+y=10$

$2x+y=10.....\left(1\right)$

$50y+5x+20x=350$

$50y+25x=350.......\left(2\right)$

Solving (1) & (2)

$50y+25x=350$

$\frac{y+2x=10}{-75x=-150}\times 50$

$x=2$

if $x=2$

$x+x+y=10$

$4+y=10$

$y=6$