You need to find the value of b so solve the first equation in terms of x:

-7b + x = 9
x = 9 + 7b

then substitute the result (9 - -7b) into the second equation:

-b + 2(9 + 7b) = 1
-b + (2 x 9) + (2 x 7b) = 1
-b + 18 + 14b = 1
-b + 14b = 1 - 18
13b = -17
b = \( \frac{-17}{13} \)
b = -1\(\frac{4}{13}\)

The Pythagorean theorem defines the relationship between the side lengths of a right triangle. The length of the hypotenuse squared (c²) is equal to the sum of the two perpendicular sides squared (a² + b²): c² = a² + b² or, solved for c, \(c = \sqrt{a + b}\)

An equation is two expressions separated by an equal sign. The key to solving equations is to repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

8a - 6a = 2a