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

-b + y = 2
y = 2 + b

then substitute the result (2 - -1b) into the second equation:

5b + 9(2 + b) = 7
5b + (9 x 2) + (9 x b) = 7
5b + 18 + 9b = 7
5b + 9b = 7 - 18
14b = -11
b = \( \frac{-11}{14} \)
b = -\(\frac{11}{14}\)

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.

An isosceles triangle has two sides of equal length. An equilateral triangle has three sides of equal length. In a right triangle, two sides meet at a right angle.

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(5a)(3ab) - (7a²)(8b)
(5 x 3)(a x a x b) - (7 x 8)(a² x b)
(15)(a¹⁺¹ x b) - (56)(a²b)
15a²b - 56a²b
-41a²b

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).