A rectangle is 4 in wide and 2 in tall. If it is enlarged to a width of 20 in, then how tall Will it be?

4

Step-by-step explanation:

It will still be 4 in. tall.  Do you mean that the parameter will remain the same?  You need to specify all constraints when asking a question (in other words: give all the details that you are given -- although I know that a lot of instructors are unnecessarily vague).  If the parameter will remain the same value then we can use the rectangle parameter formula to determine the new value for the height (aka. "length" or "how tall"):

Parameter = Length1 + Length2 + Width1 + Width2

 or

P = 2l + 2w

 so...

P = 2(4) + 2(2) = 8 + 4 = 12

 therefore...

1.   12 = 2(x) + 2(4)

2.   12 = 2x + 8

3.   12 - 8 = 2x + 8 - 8

4.   4 = 2x

5.   4 / 2 = x · 2 / 2

6.  2 = x

x = 2 in.