Question 226502
"twice one number plus a second number is 42," ---> 2x+y=42 ---> y=-2x+42

"the first number minus the second number is -6" --> x-y=-6 


x-y=-6 

x-(-2x+42)=-6 

x+2x-42=-6

3x=36

x=12 <---- first number

y=-2(12)+42=-24+42=18 <---- second number