Answer: 15
Step-by-step explanation:
varies directly means: [tex]\frac{y}{x} = k[/tex]
Plug in the given values of x and y to solve for k: [tex]\frac{21}{3} = k[/tex] → 7 = k
Next, plug in the k-value of 7 and the given y value of 105 to solve for x:
[tex]\frac{105}{x} = 7[/tex]
[tex]\frac{105}{x}(\frac{x}{7}) = 7(\frac{x}{7})[/tex]
[tex]\frac{105}{7} = x[/tex]
15 = x
The value of x when y = 105 is 15 and this can be determined by using the concept of proportionality and the given data.
Given :
The value of y varies directly with x. If x = 3, then y = 21.
The following steps can be used in order to determine the value of x when y = 105:
Step 1 - The concept of proportionality can be used in order to determine the value of x when y = 105.
Step 2 - According to the given data, the value of y varies directly with x. The mathematical expression is given below:
[tex]y \;\alpha \;x[/tex]
Step 3 - So, the above expression can be written as:
y = kx --- (1)
where k is the proportionality constant.
Step 4 - Now, substitute the value of (x = 3) and (y = 21) in the above expression.
21 = 3k
k = 7
Step 5 - Now, substitute the value of (y = 105) and (k = 7) in the expression (1).
105 = 7x
x = 15
For more information, refer to the link given below:
https://brainly.com/question/13705664
