David W. answered 07/06/17
Tutor
4.7
(90)
Experienced Prof
A quarter is worth 25¢. A dime is worth 10¢. A nickel is worth 5¢. $4 is 400¢.
If x is the number of quarters, then 25x is the value, in cents, for all those quarters. Similarly for dimes and nickels (this is the important unstated piece of information, because: 25x + 10x +5x = 400).
Now, using the distributive property on that equation,
(25+10+5)x = 400
40x = 400 [combine terms]
x = 10 [divide both sides by 40]
Checking (very important):
Is 25(10) + 10(10) + 5(10) = 400 ?
250 + 100 + 50 = 400 ?
400 = 400 ?yes