Question 772812
placement of parentheses can make a huge difference, for example you wrote this:

1-(4/x+2)÷1-(1/x-1)

which converts to

{{{1-(4/x+2)/1-(1/x-1)}}}

but I think you meant to write:

(1-4/(x+2))/(1-1/(x-1))

which converts to

{{{(1-4/(x+2))/(1-1/(x-1))}}}}

simplifying...
{{{(1-4/(x+2))/(1-1/(x-1))=((x+2)/(x+2)-4/(x+2))/((x-1)/(x-1)-1/(x-1)) }}}

{{{((x-2)/(x+2))/((x-2)/(x-1))=((x-2)/(x+2))*((x-1)/(x-2))=(x-1)/(x+2)}}}