Find the value of the argument at which the function y = 7x + 1 takes the value 15.

To solve this problem, we substitute the value of the function y = 15.
7 * x + 1 = 15;
7 * x = 15 -1;
7 * x = 14;
x = 14/7;
x = 2;
Answer: 2.
We have expanded the brackets to solve this equation. If there is a minus sign in front of the brackets, then when expanding the brackets, we change the signs of the members in the brackets to the opposite. After that, we transfer the known terms to the right, and the unknown to the left. When transferring a term from one side of the equation to another, it is necessary to change the sign to the opposite.