Final answer:
The value of y is directly proportional to the value of x. Given that y = 35 when x = 140, we can determine the proportionality constant and then find the value of y when x equals 70.
Step-by-step explanation:
The value of y is directly proportional to the value of x. This means that as x increases or decreases, y will also increase or decrease by the same factor. In this case, we have y = kx, where k is the proportionality constant.
Given that y = 35 when x = 140, we can use this information to find the value of k. Substitute the values into the equation: 35 = k * 140. Solve for k by dividing both sides of the equation by 140: k = 35/140 = 1/4.
Now, we can use the proportionality constant to find the value of y when x = 70. Substitute the values into the equation: y = (1/4) * 70 = 17.5.
Therefore, the value of y when x equals 70 is 17.5 (option a).