Question

At the beginning of every year molly deposits 200 in a savings account thst offers 20% interest annually. The total amount molly woukd have in her account after 3 years is? I got 345.60 but wrong?

Answer 1

3 years
200 * (1.2)^3 = 345.60

2 years
200 * (1.2)^2 = 288.00

1 years
200 * 1.2^1 = 240.00

It seems you calculated 200.00 for 3 years.
You need the total which equals:
345.60 + 288.00 + 240.00
= 873.60

There is a formula for this:
Total = Amount * ([(1+rate)^(years+1) -1] / rate) - amount
Total = 200 * ([(1.20^4) -1] / .20) - 200
Total = 200 * [( 2.0736 -1) / .20] -200
Total = 200 * ( 1.0736 / .20) - 200
Total = 200 *  5.368 -200
Total = 1073.6 -200
Total = 873.60