Direct and Inverse Variation: Constant of variation

State the variation the following equation represents. $r=20t$  

State the variation the following equation represents. $r=\frac{t}{20}$  

State the variation the following equation represents. $r=\frac{20}{t}$  

State the variation the following equation represents. $rt=20$  

Find the constant of variation if y varies directly with x and y = 18 and x = 6

Find the constant of variation if y varies inversly with x and y = 12 and x = 2

Find the missing value for the following variation. If y varies inversely with x and y = 4 and x = 24, find y when x = 8.

Find the missing value for the following variation. If y varies directly proportional to x and y = 16 and x = 64, find y when x = 40.

Find the constant of variation and write the function rule if y varies directly with x and y = 18 when x = 9.

Find the constant of variation and write the function rule if y varies directly with x and y = 12 when x = 6.