Which formula should be used to find the length of EF

Idon’t understand this.. will someone ? will mark brainliest along with 20 points.

Find and simplify an expression for the area of five rows of x squares with side lengths of x centimeters.

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.