The college student took 13 courses of 3 credit hours.
Step-by-step explanation:
Given,
Total credits = 59
Total courses = 18
Let,
Number of 3 credit hour courses = x
Number of 4 credit hour courses = y
According to given statement;
x+y=18 Eqn 1
3x+4y=59 Eqn 2
We will eliminate y to find the number of 3 credit hour courses, therefore,
Multiplying Eqn 1 by 4
![4(x+y=18)\\4x+4y=72\ \ \ Eqn\ 3](https://tex.z-dn.net/?f=4%28x%2By%3D18%29%5C%5C4x%2B4y%3D72%5C%20%5C%20%5C%20Eqn%5C%203)
Subtracting Eqn 2 from Eqn 3
![(4x+4y)-(3x+4y)=72-59\\4x+4y-3x-4y=13\\x=13](https://tex.z-dn.net/?f=%284x%2B4y%29-%283x%2B4y%29%3D72-59%5C%5C4x%2B4y-3x-4y%3D13%5C%5Cx%3D13)
The college student took 13 courses of 3 credit hours.
Keywords: linear equation, subtraction
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