PLEASE HELP ASAP I need the help :(

Sally deposited money into a savings account paying 4% simple interest per year.the first year,she earn $75 in interest.how much interest will she earn during the following year?

Jessa bought a yoyo from a company that claims that, with each retraction, the string rolls up by 60% of the original length. she sets up a tape measure and throws the yoyo 3 times. her data are charted below. throw length of string (feet) 1 3 2 1.8 3 1.08 jessa wants to find the sum of the length of string after 10 throws. what is the sum of the lengths, rounded to the nearest hundredth?

Find the value of x. also give me an explanation so i can complete it to other questions as well, : )