Forming equations using proportion by Boxed Rockets

Form Equations to Represent the Following

Question 1:

y is directly proportional to x, when x = 4, y = 20

y = 5 x

Question 2:

y is inversely proportional to x, when x = 2, y = 2

y = \frac{4}{x}

Question 3:

y is directly proportional to x, when x = 2, y = 4

y = 2 x

Question 4:

y is inversely proportional to x, when x = 7, y = 9

y = \frac{63}{x}