What is the grade average of 75 70 90 60 50 90 70

The average can be found by adding them all up and dividing that number by the number of items. If the result have you a number that's more than the largest or less than the lowest, you did it wrong.

(75+70+90+60+50+90+70)/7
= 505/7
=72.14

Iwould say false, not positive but if prices went up for both stores, technically there will be less buyers?

Num of plants = (original#ofplants)*(1.6)^t