a box has exactly 100 balls , and each ball is either red , blue , or white . if the box has 20 more blue balls than white balls , and thrice as many red balls as blue balls , how many white balls does the box has ?
"x = the number of red balls y = the number of blue balls z = the number of white balls from the first sentence we have equation # 1 : x + y + z = 100 . . . the box has 20 more blue balls than white balls . . . equation # 2 : y = 20 + z . . . thrice as many red balls as blue balls . . . equation # 3 : x = 3 y solve equation # 2 for z : z = y - 20 now , we can replace both x and z with y in equation # 1 3 y + y + ( y - 20 ) = 100 5 y - 20 = 100 5 y = 120 y = 24 there are 24 blue balls . this is 20 more than the number of white balls , so z = 4 . that ' s the answer . just as a check , x = 72 , and 72 + 24 + 4 = 100 . answer = 4 , ( a )"
divide(subtract(100, multiply(20, const_3)), const_4)