Question 1032769
Let me offer the single variable method, which I think is the simplest to understand and use. 
(Note - as I published, I saw Alan solved using 2 variables. You see we got the same answer. Use the method you find most comfortable to use. We proved there's often more than one way to approach a problem.)

Sarah has X dimes, they are worth 10X cents
She has (29-X) quarters, they are worth 25(29-X) cents

Her total value, is 440 cents, so 

10X+25(29-X) = 440

10X + 725 - 25X = 440

-15X = -285

X = 19 (dimes) and 29-X=10 (quarters)

19 dimes are 190 cents
10 quarters are 250 cents

440 total.