1: If the number of girls is x, then there are 4/3x= 15. So x=20. 2. Suppose the lark and the choir have X girls. X+4/3x=35, so x=20. 3: If there are X girls in the choir, then x-4/3x=5. So x=20. 4: If the mass of B is X kg, then the mass of A is 3/ 1x kg. So there is 3/ 1x+x= 12. So x=3,3/1x = 3. So a is 3. B is 9. 5: Let the number of base angles be x, then the degree of top angle is 2/1x.. So there is X+X+2/655.