81×((120c-4320)÷2×1/9+10)-50=4000
81×(120c-4320 totul pe 2 ×1/9+10)-50=4000
81(2×3×(20c-720) totul pe 2 ×1/9+10)-50=4000
81((20c-720)× 1/3+10)-50=4000
81(20c/3 -240+10)-50=4000
81(20c/3 -230)-50=4000
540c-18630-50=4000
540c=4000+18680
540c=22680
c=42
