I'm assuming your answers are listed as 1 through 4, not decimals.
You simply take 12 - 8 = 4, but ten min. less than that, so 3 hr, 50 min. then add 3 hr 45 min, totaling 7 hr 35 min. , which is closest to 7 and 1/2 hours, the second option.
I'm guessing the % of syrup refers to the % of sugar it has, therefore:
50% = 50 / 100 = 0.5
0.5 * x = 0.5
x = 0.5/0.5
x = 1
She will have 1 lbs of syrup
Simplified answer is: 13x - 15
18+3x=-10+x
3x-x=-10-18
2x=-28
x=-14
