When it says "is a less than b" , it means b - a not a-b.
x+y +z = 105
z = 10y - 11
2x = 3y + 7
Substitute expressions in terms of "y" for x and z in top equation.
[tex]\frac{3y+7}{2} + y + (10y-11) = 105 \\ \\ (3y+7) + 2y+2(10y-11) = 210 \\ \\ 25y-15 = 210 \\ \\ y = \frac{225}{25} = 9[/tex]
Substitute value of y to find x and z:
[tex]z = 10y -11 = 10(9) - 11 \\ \\ z = 79 \\ \\ 2x = 3y+7 = 3(9) +7 \\ \\ 2x = 34 \\ \\ x = 17[/tex]
