Forming equations using proportion by Boxed Rockets

Form Equations to Represent the Following

Question 1:

y is directly proportional to x, when x = 8, y = 80

y = 10 x

Question 2:

y is inversely proportional to x, when x = 8, y = 15

y = \frac{120}{x}

Question 3:

y is directly proportional to x, when x = 9, y = 126

y = 14 x

Question 4:

y is directly proportional to x, when x = 3, y = 15

y = 5 x