GG easy
I=(r)(t)(P)P=principalr=rate in decimalt=timei=interest
so just plug in what you know to solve for what you don't know
first oneI=(0.05)(3)(100)
I=15
2nd one20=(0.04)(t)(500)20=20tdivide by 20 both sides1=tt=1
3rd one35=(0.10)(7)(P)35=0.70Pdivide both sides by 3550=PP=50
4th one6=(r)(2)(200)
6=400rdivide both sides by 4000.015=rconvert to percent1.5%=r