Question

If 2x + 5y = 10 and x = 3y + 1, what is 11x + 11y?

Answer 1

You have to solve the two equations by eliminating x or y 
2x+5y=10 
x-3y=1 
Multiply all terms of second equation by two and subtract from first equation, thus eliminating x 

2x+5y-2x+6y=10-2 
11y=8 
y=8/11 
x=3y+1=3* 8/11+1=25/11 
11x+11y= 11*25/11+ 11*8/11 
= 25+8=33