simultaneous equations

Question

price of an item is ghc 3.50 when 250 items are demand, when only 50 are demanded the price rises to ghc 5.50 per item. identify the linear demand function and calculate the price per item at demand level of 115

Answer 1

kost per=5.50 if yu bi 50

kost per=3.50 if yu bi 250

delta sales/delta pries=200/-2.0=-0.01

kost per=5.50 -0.01*(how many yu bi)

at 115...5.50-0.01*115

=5.50-1.15

=4.35

Answer 2

the answer is 488.9 r4 ,,,,