How much water should be added to 18ml of 10% alcohol solution to reduce to reduce the concentration to 9%

Easy points boii. read it. ya. fresh

Aswim teacher sells lesson packages. the best deal has the highest ratio of lessons to total cost.swim lesson packagesnumber of lessons total cost$10$4010 1 $8015$80which package is the best deal? l lesson for $105 lessons for $4010 lessons for $8015 lessons for $80mark this and returnsave and exit

If 3x+8=3x+8 is it one solution or no solution