Answer:
Step-by-step explanation:
If a given variable varies directly with another variable, it means that an increase in the value of the given variable results in a corresponding increase in the value of the other variable. Also, a decrease in the value of the given variable results in a corresponding decrease in the value of the other variable.
If value of y varies directly with x, we would introduce a constant of variation so that the expression becomes
y = kx
When x = 13, y = 104. Substituting into the above expression, it becomes
104 = 13k
k = 104/13
k = 8
The equation becomes
y = 8x
Therefore, when x = 2.5,
y = 8 × 2.5
y = 20
