Hello!
The answer is:
The value of "x" is 10 feet.
Why?
To find the correct answer to this problem, we need to remember the formula to calculate the perimeteer of a rectangle, it's given by the following equation:
![Perimeter=2length+2width](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ycc184gxrlqe155uzq7hx886tbh2n1f1em.png)
Now, we are given that:
![Perimeter=200feet\\Width=30\\Length=x+60](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3rgjivmp9g5tjn16d68qa4roiybcooqgxm.png)
Then, substituting into the equation, we have:
![200feet=2(x+60feet)+2*(30feet)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ceeiigc5x90um0wutw4oo8jsdo9wrnze7v.png)
Applying the distributive property, we have:
![200feet=2x+120feet+60feet](https://img.qammunity.org/2020/formulas/mathematics/middle-school/fcnsadn1mtamw3n4sj0dgyciwx01vtyz5p.png)
![200feet-120feet-600feet=2x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/q96lm1j7lvx0chn2qb4d2oa02gikhl4k4y.png)
![2x=200feet-120feet-60feet\\\\x=(20feet)/(2)=10feet](https://img.qammunity.org/2020/formulas/mathematics/middle-school/yojjnt4puuc56awn5chchmy1a0ac3kfnnw.png)
Hence, the length of the gate is 10feet.
Have a nice day!