Brandon O. answered • 04/10/20
Bilingual psychology researcher, math and science enthusiast
So let's use some variables for this problem. If we let number of chocolates on Saturday be S, number of Chocolates on Friday be F, and number of Chocolates on Thursday be T, we know that S = 2F because Saturday sold twice as many as Friday. Thursday had 20 more chocolates than Friday so we T = 20 + F. In total, 1980 chocolates were sold (T + F + S = 1980). We can substitute some variables to solve for one of them.
T = 20 + F
S = 2F
T + F + S = 1980
Let's choose to isolate F in the first equation: F = T - 20
Then we can plug this into the second equation: S = 2*(T - 20)
T = 1980 - F - S
= 1980 - (T - 20) - 2*(T-20)
= 1980 - T + 20 - 2T + 40
T = 1980 - 3T + 60
4T = 2040
T = 2040/4
T = 510
Number of chocolates sold was 510 on Thursday. You can then plug this number into the first equations to check our work.
