STEP 1:
identify variables and equations
x= larger number
y= smaller number
FIRST EQUATION
x + y= 42
SECOND EQUATION
y= 2x - 63
STEP 2:
substitute the y value in second equation in for y in first equation
x + y= 42
substitute y value from 2nd equation
x + (2x - 63)= 42
combine like terms
3x - 63= 42
add 63 to both sides
3x= 105
divide both sides by 3
x= 35 larger number
STEP 3:
find y value; substitute step 2 x value into either original equation
x + y= 42
35 + y= 42
subtract 35 from both sides
y= 7 smaller number
ANSWER: larger number is x= 35; smaller number is y= 7.
Hope this helps! :)