Coordinates of Q
On a straight line, a gradient of 2 means that for every step to the right, you go 2 steps up. Therefore, Q has coordinates \((5.75, 9.238)\). There is no need to work out the intercept, \(c\).
Coordinates of R
R has coordinates \((3.75, 5.238)\).
Coordinates of S
S has coordinates \((5.25, 8.238)\).