Aaron has 3 brothers(Brendan, Cole, Devin) Brendan is 2 times Cole's age. The sum of Aaron and Devin's age equals Brendan's age. The sum of Cole and Devin's age equals Aaron's age. The sum of all 4 brothers equals 40. Show equation and each brother's age.

Devin is 4. Cole is 8. Brendan is 16. Aaron is 12. I used each variable according to the beginning of their name. So B=2C. A+D=B. therefore A+D=2C. C+D=A. therefore, from the previous two equations, C+2D=2C. then 2D=C. and we also know a+b+c+d=40. so i took a+b+3d=40. and we know b=2c and that 2c equals 4d. so a+7d=40. then we know a=d+c and 2d equals c. so now it is a=3d. so 10d equals 40. divide by 10 it is now d=4. and we know 2d=c so 2(4)= coles age. cole is 8. then we know 2(8) equals b which is 16. then lastly 4+8=a which is 12. i can explain better if needed

On monday,mrs.wise bought 3 lbs of apples at $4per lb= 4*3=$12on tuesday ,20%off and she buy 5 lbs of apples = $4-20%=3.20*5lb=$16example: other wise when she buy 5lbs on monday she have to spend 4*5=20