two alloys a and b are composed of two basic elements . the ratios of the compositions of the two basic elements in the two alloys are 7 : 5 and 1 : 2 , respectively . a new alloy x is formed by mixing the two alloys a and b in the ratio 4 : 3 . what is the ratio of the composition of the two basic elements in alloy x ?
"mixture a has a total of 7 + 5 = 12 parts . if in the final mixture this represents 6 parts , then the total number of parts in mixture b should be ( 12 / 6 ) * 3 = 6 . so , we should take of mixture b a quantity with 3 and 6 parts , respectively . this will give us in the final mixture ( 7 + 3 ) : ( 5 + 6 ) , which means 10 : 11 answer d ."
divide(add(multiply(4, 7), multiply(5, divide(add(7, 5), const_2))), add(multiply(4, 5), multiply(5, divide(add(7, 5), const_2))))