Chapter 9 - Section 9.1 - Solving Systems of Linear Equations in Three Variables and Problem Solving - Exercise Set - Page 639: 32

33.3 million women in swimming, 17.2 million women in running

swimming had 1.1 million less than twice the number in running total of swimming and running was 50.5 million $x$ is swimming, $y$ is running $x=2y-1.1$ $x+y=50.5$ $x+y=50.5$ $2y-1.1+y=50.5$ $3y-1.1=50.5$ $3y-1.1+1.1=50.5+1.1$ $3y=51.6$ $3y/3=51.6/3$ $y=17.2$ $x=2y-1.1$ $x=2*17.2-1.1$ $x=34.4-1.1$ $x=33.3$