Mat 116
posted by Robin .
substitution method
7x +9y= 19
x=255y
I read over all the problems I do not see any errors I can find.
Please point this out!
After this I have another problem
0.1<4
0.1 X 100 < 4
10< 4
10 4
_______
10 10
{x<  4/10 or 0.4

Substitute 255y for x in the first equation and solve for y. Put that value in the second equation to find x. Check by putting both values into the first equation.
It is not clear what the second problem is or what you are doing with the second problem.