Astudent received a 75% on an exam. if there were 20 questions on the exam, which ratio would show the number of questions answered correctly to the total number of questions? a. 20: 5 b. 5: 20 c. 15: 20 d. 20: 15

For this case what you can do is the following rule of three:
 100% ---> 20
 75% > x
 Clearing the value of x we have:
 x = (75/100) * (20)
 x = 15
 This number represents the number of correct answers.
 We have then that the ratio is:
 15:20
  
 A ratio that would show the number of questions answered correctly to the total number of questions is: 
 C. 15:20

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)