She made $2.5 from hitting drums because 10 - 7.5 = <<10-7.5=2.5>>2.5
She hit 200 drums to start making money
She hit 100 drums in order to make the $2.5 because 2.5/.025 = 100
She hit 300 drums in total because 100 + 200 = <<100+200=300>>300
#### 300