The perimeter is all sides length added together. You can make an equation:5+5+x+x where x is the length.
5+5=10 18-10=8 There is two sides so you do eight divided by two
The length is 4
Hello.
In 10 years, his age will be

The sum of his current age and 10 equals his age in 10 years.
2 years ago his age was

The difference of his current age and 2 equals his age 2 years ago.
7 years ago his age was

The difference of his current age and 7 equals his age 7 years ago.
Therefore, his age after 10 years will be
, his age 2 years ago was
, and his age 7 years ago was 
I hope it helps.
Have a nice day.

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Answer:
The length is 28 and the width is 11
Step-by-step explanation:
To solve this problem, we can make the width as x.
Since the length is 5 less than 3 times the width, it's going to be 3x - 5
So now we've got the length and width, just need to find the perimeter, which is all the sides added up together. They already gave us the perimeter, so we just have to solve the equation:
2(3x - 5) + 2x = 78
6x - 10 + 2x = 78
8x - 10 = 78
8x = 88
x = 11
x = 11, but remember, x is the width, not the length. Since we already found what x is, we just have to plug it into the equation of:
3x - 5
3 × 11 - 5
33 - 5 = 28
Answer: Length = 28 (don't forget to add the unit if there is one)