A chemical company makes two brands of antifreeze. The first brand is 35% pure antifreeze, and the second brand is 85% pure antifreeze. In order to obtain 140 gallons of a mixture that contains 70% pure antifreeze, how many gallons of each brand of antifreeze must be used?​

Scott harris can invest $7,000 in a 1-year cd that earns interest at an annual rate of 4 percent compounded monthly. the amount per $1.00 is 1.040742. he can also invest $7,000 in a 1-year cd at annual rate of 4 percent compounded quarterly. the amount per $1.00 is 1.040604. what is the difference in the amount of interest earned for each investment? a) $0.96 b) $0.81 c) $0.87 d) $0.88

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

How do you solve a question like this?