How do you solve the following system?: # 7x +5y =-15 , -4x -9y = 5#
There is no single variable, so using the method of substitution will lead to some uncomfortable math.
Let's use the elimination method.
Make additive inverses. I have chosen the x terms for this.
Substituting for x and y in B gives 5.
Despite the awkward fractions, the method remains the same.