The number of green markers is thrice the number of red markers. The number of red markers is 7 more than the number of blue markers. The total number of markers is 113. The cost of each green marker is $3.70 and the cost of each blue marker is $1.60. The total cost of all the markers is $346.40.

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

(a)
Number of blue markers = 1 u
Number of red markers = 1 u + 7

Number of green markers
= 3(1 u + 7)
= 3 u + 21

Total of number of markers
= 1 u + 1 u + 7 + 3 u + 21
= 5 u + 28

5 u + 28 = 113
5 u = 113 - 28
5 u = 85

1 u = 85 ÷ 5 = 17

Number of blue markers
= 1 u
= 17

(b)
Number of blue markers = 17

Number of red markers
=  17 + 7
= 24

Number of green markers
= 3 x 24
= 72

Cost of blue markers 
= 17 x 1.60
= $27.20

Cost of green markers 
= 72 x 3.70
= $266.40

Cost of red markers
= 346.40 - 266.40 - 27.20
= $52.80

Cost of 1 red marker
= 52.80 ÷ 24
= $2.20

Answer(s) (a) 17; (b) $2.20