Step 1: rearrange the second equation for y. Step 2: substitute y from the second equation into the first equation. Step 3. Calculate y.
Step 1. <span>The second equation is: 6x + 3y = 90 Divide both sides of the equation by 3: (6x + 3y)/3 = 90/3 6x/3 + 3y/3 = 30 2x + y = 30 Rearrange the equation: y = 30 - 2x
Step 2. </span>Substitute y from the second equation (y = 30 - 2x) into the first equation: <span>15x + 9y = 240 15x + 9(30 - 2x) = 240 15x + 270 - 18x = 240 15x - 18x = 240 - 270 -3x = -30 x = -30/-3 x = 10
Step 3. Since </span>y = 30 - 2x and x = 10, then: y = 30 - 2 * 10 y = 30 - 20 y = 10