1 + 2 + 3 + 4 + 5 + 6 = 21 . :)
Doesn't it say the answer in that question...
It is asking for the actual cost of the item and it said $1,489
for his set.
Lets get started :)

We can cross multiply, to find the value of x
3x = 7 x 5
3x = 35
We have to divide by 3 on either sides to isolate x

3 and 3 cancels out
x =

Then, x +

( 7 divided by 7 is 1)

+ 1 =
Proportional reasoning is the ability to compare two things using information given, in math, it is most frequently defined as comparing quantities. For something to be proportional, there has to a constant ration of another quantity.