You earn $7 for every ⅓ hour you cut the grass. How much money do you make for 3 hours?

[math_celebrity]

You earn $7 for every ⅓ hour you cut the grass. How much money do you make for 3 hours?

3 hours / 1/3 hour = 9 (1/3 blocks)

So we have:
7 * 9 = 63