The number of brown markers is twice the number of orange markers. The number of orange markers is 5 more than the number of blue markers. The total number of markers is 139. The cost of each brown marker is $2.80 and the cost of each blue marker is $2.40. The total cost of all the markers is $362.40.

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

(a)
Number of blue markers = 1 u
Number of orange markers = 1 u + 5

Number of brown markers
= 2(1 u + 5)
= 2 u + 10

Total of number of markers
= 1 u + 1 u + 5 + 2 u + 10
= 4 u + 15

4 u + 15 = 139
4 u = 139 - 15
4 u = 124

1 u = 124 ÷ 4 = 31

Number of blue markers
= 1 u
= 31

(b)
Number of blue markers = 31

Number of orange markers
=  31 + 5
= 36

Number of brown markers
= 2 x 36
= 72

Cost of blue markers 
= 31 x 2.40
= $74.40

Cost of brown markers 
= 72 x 2.80
= $201.60

Cost of orange markers
= 362.40 - 201.60 - 74.40
= $86.40

Cost of 1 orange marker
= 86.40 ÷ 36
= $2.40

Answer(s) (a) 31; (b) $2.40