Question

Solve 2x + 5y = 20; 3x - 10y = 37 by elimination. How do you do this? Thank-you!

Answer 1

$\left\{\begin{array}{ccc}2x+5y=20&\text{multiply both sides by 2}\\3x-10y=37\end{array}\right\\\\\underline{+\left\{\begin{array}{ccc}4x+10y=40\\3x-10y=37\end{array}\right}\qquad\text{add both sides of the equations}\\.\qquad7x=77\qquad\text{divide both sides by 7}\\.\qquad\boxed{x=11}\\\\\text{Put the value of x to the first equation:}\\\\2(11)+5y=20\\\\22+5y=20\qquad\text{subtract 22 from both sides}\\\\5y=-2\qquad\text{divide both sides by 5}\\\\\boxed{y=-\dfrac{2}{5}}\\\\Answer:\ \boxed{x=11\ and\ y=-\dfrac{2}{5}}$