Question

5. Samantha has 30 coins, consisting of 20c and 50c, which total $13.50. How many of each does she have?​

Answer 1

50c = 25

20c = 5

Explanation:

50x + 20y = 1350 (1) - multiply y by one.

x + y = 30 (2) - multiply y by 20.

50x + 20y = 1350 (1)

20x + 20y = 600 (2)

If you treat it like simultaneous equations, you take away equation 2 from equation 1.

30x = 750

x = 25

Then, once you have your value of x, you can substitute it back into the original equations to find your answer.

x + y = 30

25 + y = 30

y = 5

Then you have your answer. Hope this helps :)