A shop stocks 30 bottles of shampoo. Felix buys 2/5 of bottles and Anita buys 3/10 of the bottles. How many bottles of shampoo does the shop have left?

9 bottles of shampoo left.

Why?

Let x represent the number of bottles of shampoo that the shop has left.

Let f represent the number of bottles of shampoo Felix buys.

Let a represent the number of bottles of shampoo Anita buys.

This means that x = 30 - (f + a)

So, f = (2/5) * 30

f = 12

So, a = (3/10) * 30

a = 9

Plug it into our equation;

x = 30 - (f + a)

x = 30 - (12 + 9)

x = 30 - 21

x = 9

Therefore, the shop has 9 bottles of shampoo left.