A shop sells “Gello” pens and “Inko” pens. A “Gello” pen costs £5 and an “Inko” pen costs £7. One day the shop sold 17 pens and recieved £109. How many of each type of pen were solved?
+23246 Let G = number of Gello pens and K = number of Inko pens.
Number equation: G + K = 17
Value equation: 5G + 7K = 109
G + K = 17 ---> K = 17 - G
Substituting: 5G + 7K = 109 ---> 5G + 7(17 - G) = 109
5G + 119 - 7G = 109
-2G = -10
G = 5
Since G + K = 17 and G = 5, K = 12.
