Apicture frame originally priced at $13.00 is on sale for $7.50. what is the percent of decrease, rounded to the nearest whole number?

a. 35%
b. 37%
c. 42%
d. 55%

"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