We want everything in terms of p so that there is only one unknown variable.If Tom scored 3x what John did, Tom scored 3 x p. This can be written as 3p.Their total marks are 188 so p (John's marks) + 3p (Tom's marks) = 188.Therefore 4p = 188To find p, we must divide 4p by 4 and because 4p = 188 is an equation, we have to do the same thing to both sides.This means that p = 188 / 4So p = 47Tom scored 3p so 3p = 3x 47 = 141