-x²+61x+78.2≥67.5
-x²+61x+10.7≥0
x²-61x-10.7≤0
x²-61x+(61/2)²-3721/4-107/10≤0
(x-61/2)²-18605/20-214/20≤0
[x-61/2-√(18819/20)][x-61/2+√(18819/20)]≤0