How do i solve this? can you show me step by step process.

(Q14) To find the equation when given the gradient and one set of points (or coordinates), you have to solve for b. 
1. Identify the gradient and x- and y- intercepts. 
    m=3, x=1, y=5
2. Substitute them into the equation, y=mx+b. 
    5=3(1) + b 
3. Solve for b.
    5=3 + b 
    b=2 
4. Rewrite the equation. 
   y=3x+ 2
(Q15) To find the equation when given two sets of points, you need to.
1. Find the gradient, using the formula, (x2-x1 / y2-y1) 
   (7,5) and (4, -7)
    x1=7, x2= 4, y1=5, y2=-7
    4-7/-7-5 = -3/-12 = 1/4 
   Therefore, gradient = 1/4 
2. Substitute with one set of points (can be either (7,5) or (4,-7) in this example - question 15) into the equation, (like you did in question 14) 
  a) Identify the gradient and x- and y- intercepts. 
   m=1/4, x=7, y=5
  b) Solve for b. 
   5=1/4(7) + b
   5=7/4 + b 
   b=13/4 or 3 1/4 
  c) Rewrite the equation.
   y=1/4x + 13/4