Question

X is partly constant, and partly varies as y. When y= 2 , x = 30 and when y = 6, x = 50

Answer 1

"X is partly constant and partly varies as y"

---> x = ky + p

when y=2,x=30 ---> 30 = 2k + p

when y=6,x=50 ---> 50 = 6k + p

subtract: 20 = 4k

k = 5

sub back in the first: 30 = 10+p

p = 20

x = 5y + 20

now you can answer B

notice this is just a variation of y = mx + b

Answer 2

"X is partly constant and partly varies as y"

---> x = ky + p

when y=2,x=30 ---> 30 = 2k + p

when y=6,x=50 ---> 50 = 6k + p

subtract: 20 = 4k

k = 5

sub back in the first: 30 = 10+p

p = 20

x = 5y + 20

now you can answer B

notice this is just a variation of y = mx + b