If a graph is proportional then the line will go through the origin at point (0, 0). If the equation is proportional then it will be in the form of y=kx with no other operations after. The constant of proportionality is another way to say the slope and in your specific equation the slope would be 1/5.
25 x 0.1 = 2.5 ≈ 3
25 + 3 = 28
The machinist would make about 28 on Wednesday
