Please help me find the missing measurement!

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.

Ineed with number 6 , explain how to get 1978

The number of fish in a lake can be modeled by the exponential regression equation y=14.08 x 2.08^x where x represents the year