It’s bevause you can see what you are doing instead of doing it all of your head which could get messed up.
I’m pretty sure the answer is -1
3:5=x:50
Therefore 5 ×x = 50
x = 10
Therefore 3 × 10 = 30
therefore 30 blue pens
proof = 30 blue + 50 red= 3+ 5
therefore 80 = 8x
2.5 4/5 8% that is an example of written fractions decimal and percents
Answer:
$3125
Step-by-step explanation:

A = 250(1 + 0.25)ⁿ
A = (312.5)ⁿ
n = 10
A = $3125
A = I