Fatimah has 40 coins. Some of the coins are 50c coins and the rest are 20c coins. The total value is $16.10. How many 50c coins does Fatimah have?

number of 50c = x

number of 20c = y

total coins 40

x +y = 40 (1)

0.5x + 0.2y = 16.10 (2)

from (1) => x = 40 - y

substitute x in (2)

0.5(40 -y) + 0.2y = 16.10

20 - 0.5y + 0.2y = 16.10

-0.3y = -3.9

y = 13

from (1) => x = 27

number of 50c = 27 coins

after simplifying it i got: -36.25 as my answer. hope that !