The number of blue markers is twice the number of orange markers. The number of orange markers is 9 more than the number of green markers. The total number of markers is 115. The cost of each blue marker is $4.10 and the cost of each green marker is $2.70. The total cost of all the markers is $391.10.

1. Find the number of green markers.
2. Find the cost of a orange marker.

(a)
Number of green markers = 1 u
Number of orange markers = 1 u + 9

Number of blue markers
= 2(1 u + 9)
= 2 u + 18

Total of number of markers
= 1 u + 1 u + 9 + 2 u + 18
= 4 u + 27

4 u + 27 = 115
4 u = 115 - 27
4 u = 88

1 u = 88 ÷ 4 = 22

Number of green markers
= 1 u
= 22

(b)
Number of green markers = 22

Number of orange markers
=  22 + 9
= 31

Number of blue markers
= 2 x 31
= 62

Cost of green markers 
= 22 x 2.70
= $59.40

Cost of blue markers 
= 62 x 4.10
= $254.20

Cost of orange markers
= 391.10 - 254.20 - 59.40
= $77.50

Cost of 1 orange marker
= 77.50 ÷ 31
= $2.50

Answer(s) (a) 22; (b) $2.50