let's do 15 first.
From the model, we can conclude that 3x + 6 + 9x - 8 = 142. We then solve:
12x - 2 = 142 => 12x = 144 => x = 12
Then we complete the equations and solve to get:
3x + 6 = 42 and 9x - 8 = 100
Now number 16.
We can conclude from the model that 12x + 3 + 6x - 3 = 90. We solve to get:
18x = 90 => x = 5
Then we complete the equations and get:
12x + 3 = 63 and 6x - 3 = 27
So, for 15, 3x + 6 = 42 and 9x - 8 = 100. For 16, 12x + 3 = 63 and 6x - 3 = 27.
Hope this helps!