Diego is attending UTEP and has completed some courses worth 3 credits and some course worth 4 credits. he has earned a total of 59 credits after completing 18 courses. How many courses worth 4 credits has Diego completed

3 credit course = 13

4 credit course = 5

Step-by-step explanation:

Given that :

Total credits = 59

Total courses = 18

Let :

Number of 3 credit course = x ; number of 4 credit course = y

x + y = 18 - - (1)

3x + 4y = 59 - - - (2)

x = 18 - y

3(18 - y) + 4y = 59

54 - 3y + 4y = 59

54 + y = 59

y = 59 - 54

y = 5

x = 18 - 5

x = 13

3 credit course = 13

4 credit course = 5

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