Forming equations using proportion by Boxed Rockets

Form Equations to Represent the Following

Question 1:

y is directly proportional to x, when x = 11, y = 99

y = 9 x

Question 2:

y is inversely proportional to x, when x = 11, y = 5

y = \frac{55}{x}

Question 3:

y is inversely proportional to x, when x = 3, y = 7

y = \frac{21}{x}

Question 4:

y is directly proportional to x, when x = 1, y = 12

y = 12 x