Together Larry and Lenny have $\$$35. Larry has two-fifths of Lenny's amount. How many more dollars than Larry does Lenny have?

Let A be the amount that Lenny has....then Larry has (2/5)A   ...and together they hae $35  ....so....

A + (2/5)A = 35     simplify

(7/5)A  = 35     multiply both sides by 5/7

A = (5/7)*35 = $25....this is the amount Lenny has

So Larry must have $(35 - 25) = $10

Thus....Lenny has $15 more than Larry