Răspuns:
1n+n×[(3la5)-3la12:3la9×3la7]=2la0
1n+n×(3la10-3la12:3la9×3la7)=1
1n+n×(3la10-3la3×3la7)=1
1n+n×(3la10-3la10)=1
1n+n×0=1
n=1