If you mean: 2x-5y+2z = 16 and 3x+2y-3z = -19 and 4x-3y+4z = 18 then the solutions are found as follows:-
3(2x-5y+2z = 16) => 6x-15y+6z = 48
2(3x+2y-3z = -19) => 6x+4y-6z = -38
Adding the above: 12x-11y = 10 thus eliminating z
4(3x+2y-3z = -19) => 12x+8y-12z = -76
3(4x-3y+4z = 18) => 12x-9y+12z = 54
Adding the above: 24x-y = -22 thus eliminating z
2(12x-11y = 10) => 24x-22y = 20
1(24x-y = -22) => 24x-y = -22
Subtracting the above: -21y = 42 thus eliminating x
If: -21y = 42 then y = -2
So by substitution: x = -1, y = -2 and z = 4
Check: (2*-1)-(5*-2)+(2*4) = 16
Check: (3*-1)+(2*-2)-(3*4) = -19
Check: (4*-1)-(3*-2)+(4*4) = 18
The LCM of 2x5y and 4x3y2 is 4x5x3y2 = 60xy2.
It is any fraction where the denominator is a multiple of non-negative integer powers of 2 and 5. In other words, a fraction with a denominator of the form 2x5y where x and y are non-negative integers.