If y varies directly with x, and y =9 when x=3, what is x when y=15

directly varies for that mean if y increases x will increase too and the other way around if y decreases x will decrease too.

an easy way to solve this is to make all values into fraction ik it sounds confusing lemme explain it. so if we say and add the values of the known we can say that if is equal to

now we just solve it for x

hence when y is 15 x will be 5

the formula of a slope:

from a table we have

substitute:

the slope of f(x) is -1.

the graph of funcfion g(x) is a horizontal line. the slope of a horizontal line is equal 0. therefore the slope of g(x) is 0.

-1 < 0