Interest Problem?

Question

Not homework. Studying for test. I have the answer just get lost getting there.

Suppose $20,000 was invested, part in a stock expected to pay 7.5% interst over 2 years and the balance in bonds paying 5.4% interest for 2 years. If the total interest earned in 2 years was $1227, how much was invested in each stock.

Answer is supposed to be
Stock: 7000 Bond: 13000

Answer 1

LET X = AMOUNT INVEST AT 7.5%
LET Y = AMOUNT INVESTED AT 5.4%
SO X + Y = 20000
AND 2(.075)(X) + 2(.054)(Y) = 1227 WHICH BECOMES
.15X + .108Y = 1227
BY SUBSTITUTION .15X + .108(20000-X) = 1227
SOLVING FOR X = 7000 AND Y= 13000

Answer 2

Simple or compound intrest..?

Assume x is invested in bonds...and therefore 20000-x is invested in stocks.

For simple intrest, Interest = P N R /100

For compund Intrest .Interest= P{(1+R)^N}