You can use the fact that summing something P times is equal to multiplying that thing with P.
Those who could save the needed amount were:
Option A: A and C
<h3>How to add something P times?</h3>
Let you have to add a value y p times. Then you write it as:

<h3>How to calculate how much each friend earned?</h3>
checking total money each friend earned:
- Friend A : worked 13 hours per week at $6.95/hour rate.
Since in 1 week, A works 13 hour, thus, in 8 weeks, he works

Each hour he earns $6.95, thus, for 184 hours, he will earn

Similarly,
- Friend B: worked 15 hours per work at $5.85/hour rate
B earned 
- Friend C: worked 18 hours per work at $5.25/hour rate
B earned 
- Friend D: worked 11 hours per work at $7.80/hour rate
B earned 
Only friend A and friend C could earn more than or equal to $750
Thus,
Those who could save the needed amount were:
Option A: A and C
Learn more about multiplication here:
brainly.com/question/520497