I have no clue on how to solve this mutual funds problem please help !!

Question

Juan had $21100 and chose to split the money into two different mutual funds. During the first year, Fund A earned 5% interest and Fund B earned 3% interest. If he received a total of $829 in interest, how much had he invested into each account? 

Answer 1

If this is simple interest, then let a = fraction invested in Fund A and b = fraction invested in Fund B

then 21,100a(.05) + 21,100b(.03) = $829 and a + b = 1

1055a + 633b = 829

a + b = 1

Solving simultaneously, we find that a = .46 and b = .54

So, .46(21,100) = $9706 (Fund A) and .54(21,100) = $11,394 (Fund B)