Answer:
AB = 11
Explanation:
Given:
AB = 3x-1; BC = x+3; AC = 18
Since, AB and BC are parts of AC, we can conclude that AC is the sum of AB and BC.
Therefore, we have the following as an equation:
AB + BC = AC
Substitute each values;
(3x-1) + (x+3) = 18
Then solve for x;
(3x-1) + (x+3) = 18
4x + 2 = 18 //Combine like terms; 3x + x = 4x; 3 + (-1) = 2
4x = 18 - 2 //Since we want to solve the x, we want to let it alone, that's why we move the 2 to the other side (moving an expression past an equal changes its sign)
4x = 16
4x/4 = 16/4 //Divide both by four
x = 4
Now, substitute the x;
AB = 3x-1
AB = 3(4)-1
AB = 11
If you substitute the value of x such as four here;
(3x-1) + (x+3) = 18
(3(4)-1) + (4+3) = 18
11 + 7 = 18
18 = 18 //Checking