Sherrie receives 5 times as many phone calls as carrie, and carrie receives 5 less calls than mary. if the total number of combined calls for them was 68 how many calls did mary receive?

let g, r and l be the calls received,

r=c−5 and g=5b=5(c−5)=5c−25

So, g+r+l=7c−30=68,
7c = 98. c = 14

Mary received 14 calls.

"standard form:

3x2 + 14x − 10 = 0

solutions based on quadratic formula:

x1   = −14 − √ 142 − 4×3×(−10) /   2×3   = −14 − 2 × √ 79 /   6   ≈ −5.296

x2   = −14 + √ 142 − 4×3×(−10) /   2×3   = −14 + 2 × √ 79 /   6   ≈ 0.629