When we use past simple and present perfect?

Y=4x^2+x-1 solve using quadratic formula

The sum of two numbers is 58. the first number is 8 less than half the second number. let  c  represent the first number. let  drepresent the second number. which statements about solving for the two numbers are true? check all that apply.the equation    represents the sum of the two numbers.the equation    represents the sentence “the first number is 8 less than half the second number.”the equation    represents the relationship between the two numbers.the equation    represents the sum of the two numbers.the number  d  is 14.the number  c  is 44.the number  c  is 14.the number  d  is 44.

Adepartment store purchases screen-printed t-shirts at a cost of $5 per shirt. they mark up the price 150% (making the selling price 250% of the store's purchase price) and put them on the sales floor. every month that a t-shirt doesn't sell, the store reduces the selling price by 25%.