Forming equations using proportion by Boxed Rockets

Form Equations to Represent the Following

Question 1:

y is directly proportional to x, when x = 10, y = 150

y = 15 x

Question 2:

y is directly proportional to x, when x = 12, y = 36

y = 3 x

Question 3:

y is inversely proportional to x, when x = 3, y = 10

y = \frac{30}{x}

Question 4:

y is directly proportional to x, when x = 2, y = 10

y = 5 x