Explicație pas cu pas:
Nu exista formula, desfiintezi parantezele si rezolvi ecuația
(1-x)+(1-2x)+(1-3x)+(1-4x)+(1-5x)+(1-6x)+(1-7x)+(1-8x)+(1-9x)+(1-10x)=100
-> 1-x+1-2x+1-3x+1-4x+1-5x+1-6x+1-7x+1-8x+1-9x+1-10x=100
->adunam terminii de acelasi fel
->10-55x=100
->-55x=100-10
-> -55x=90
-> x=-90/55
-> x= -18/11
