that's all , all the best
So what you need to do is find the less he can use.
0.10r + 0.20b = 24
3r = b + 20....b = 3r - 20
0.10r + 0.20(3r - 20) = 24
0.10r + 0.60r - 4 = 24
0.70r = 24 + 4
0.70r = 28
r = 28/0.70
r = 40 <=== there are 40 reds
0.10r + 0.20b = 24
0.10(40) + 0.20b = 24
4 + 0.20b = 24
0.20b = 24 - 4
0.20b = 20
b = 20/0.20
b = 100 <=== there are 100 blues
200,000 is ten times 20,000
It’s the second, the penultimate and the last one :)
3(2 + x)
x + 2x + 2 + 4
x + x + x + 1 + 1 + 1 + 1 + 1 + 1
