2/3=1/2x+2y can someone help

Fractions can be added and subtracted only if they're fractions. a. like b. proper c. improper d. unlike

Three times the sum of a number and seven is negative thirty-six. what is the number?

The half-life of a certain material is 0.004 second. approximately how much of a 20-gram sample will be left after 0.016 second? a. 5 grams b. 16 grams c. 0.32 gram d. 1.25 grams