so you know the formula for average here would be (testscore1 + testscore2 + testscore3 + testscore4)/4
the scores for the first three are given, we have to find the last using an inequility. since we want the average to be at least 70 to get a C, we have:
Let the final score Sam needs for a C be x
then (75 + 63 + 68 + x)/4 >= 70
=> 206 + x >= 280
so x >= 74
so Sam's final score has to be at least 74 to get a C (or above) according to the above inequality.
2. The cost for a long-distance telephone call is $0.36 for the first minute and $0.21 for each additional minute or portion thereof. Write an inequality representing the number of minutes a person could talk without exceeding $3.
Let x be the additional minutes we can talk for to not exceed a $3 bill. So the total number of minutes we can talk without exceeding $3 is x+1 minutes.
we want 0.36 + 0.21x <= 3
=> 0.21x <= 2.64
=> x <=2.64/.21
=> x <= 12.57
so if y is the total number of minutes we can talk
y <= x + 1
=> y <= 13.57