[—–u——]  —> $2

[——u—–]  —> $5

2u + 5u = 280

7u = 280

u = 40

Number of $2 = Number of $5 = 40

38. Let A be the number of apples Bala bought.

3/5 A = 30
A = 50 #

Let me try with equations.

2n + 5n = 280
7n = 280
n = 40

So number of $2 notes = 40 #