Chapter 4 - Section 4.2 - Solving Systems of Linear Equations in Three Variables - Exercise Set - Page 220: 29

Two Numbers are $30$ and $15$.

Let two numbers be $x$ and $y$. Sum of two numbers is $45$ $x+y = 45$ Equation $(1)$ One number is twice the other. $x= 2y$ Equation $(2)$ Substituting $x$ in Equation$(1)$ $x+y = 45$ $2y+y = 45$ $3y = 45$ $y = \frac{45}{3}$ $y = 15$ Substituting $y$ value in Equation$(2)$ to get $x$ $x= 2y$ $x= 2(15)$ $x= 30$ Two Numbers are $30$ and $15$.