You add the total number of balls, which is 10. and then it is asking for brown balls and looking at the equation you know there are 3. so 3/10 is .30 which is 30%
Start by distributing the 4: 12-8x=15 Add 8x to both sides of the equation and subtract 15 from both sides: 8x=-3 divide both sides by 8 to get the value of x: x=-3/8