At what value of the argument does the function y = -3x + 2 take on a value equal to -2.5?

The value of the argument is the value of the variable x. The function is the value of the variable y. In order to find the value of the argument, when the function y = -3x + 2 takes a value equal to -2.5, you need to substitute the number -2.5 instead of the variable y and solve the equation for x. We get:
-2.5 = -3x + 2;
3x = 2 + 2.5;
3x = 4.5;
x = 4.5: 3;
x = 1.5.
Answer: the value of the argument is equal to the decimal fraction 1.5.