Y someone talk to me Lol

By what percent will the product of two numbers change, if the first number increases by 70%, while the second number decreases by 40%.

It's 90 °f in the shop with high humidity. what pressure will be shown on the high-side pressure gauge (ac system on)?             a.  10 to 50 psi    b.  40 to 140 psi  c.  210 to 290 psi  d.  at least 350 psi

Two technicians are discussing how to test a car's exhaust by holding a small piece of paper within an inch of the tailpipe mouth. technician a says that if the paper is vibrating due to a "puffing" output from the tailpipe, this signals a smoothly running engine. technician b says that if the paper is being drawn toward the tailpipe, this could indicate burned exhaust valves. who is correct? a. technician b b. both technicians a and b c. technician a d. neither technicians a or b