How many solutions does this equation have?

Marco has $38.43 dollars in his checking account. his checking account is linked to his amazon music account so he can buy music. the songs he purchases cost $1.29. part 1: write an expression to describe the amount of money in his checking account in relationship to the number of songs he purchases. part 2: describe what the variable represents in this situation.

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)