There are 12 red and blue pencils on a desk. there are twice as many red pencils as blue pencils. how many read pencils are there on the desk?

r+b =12

r =2b  (twice as many red as blue)

substitute r = 2b into r+b=12

2b + b = 12

3b =12

divide by 3

b=4

r = 2b

r=2(4)

r=8

There are 4 blue pencils and 8 red pencils

step-by-step explanation:

c.

step-by-step explanation:

she should of added 9^2 and 12^2. that is because it is a^2+b^2=c^2. c^2 is the hypotenuse and should always be bigger than the other two numbers. which is why she should of added 9 squared and 12 squared together instead of 15 squared.