Michelle's Problem Solving

I am learning to draw a picture to help me solve a problem.

The problem that I had to solve was:

Larenzo has 3 times as many marbles than Janet does. Janet has 7 marbles. How many marbles does Larenzo have?

Miss Hughes came and did some maths with us. I drew three boxes and seven marbles and I got 21. It was a little bit tricky.