Ireally need an answer that makes sense to numbers 6,7,8, and 9 if you answer this question by thursday then i will promise you a brainlist )

6. green is 30 cm. black is 20cm

90 cm broken down into a ratio of 3: 4: 2 means that you divide 90 by 9 (3+4+2=9). 90/9 is 10. this means one ninth of this ratio is 10. so, green in the ratio is 3, so 3*10= 30 cm. the ratio of black pole is 2, so 2*10 is 20 cm.

7. cement is 3.43 m cubed and sand is 6.86 m cubed. 
you would use the same method as 6, just replace with your new given variables. 

8. there is 102kg among all the boys weights total.

since ryan is 30kg, and is 5 in the ratio, we can simply divide 30 by 5 to give us 6kg for 1 in the ratio. now, we add the total ratio. 8+5+4=17. 17*6 gives us 102kg in total.

9. the largest amount of money is $75

this is probably the simplest to find once you understand how to do the rest, since 2 is the smallest ratio, and 2 is $30, divide 30/2=15. this means that 15 is 1 in the ratio. since 5 is the largest ratio number, multiply 15 by 5 to get 75.