Answer:
6 years
Step-by-step explanation:
So each person's age can be represented as a linear equation, since each year our age increases by 1. It can be represented in the slope-intercept form: y=mx+b. The slope in this case is going to be 1, since the time is going to be years, and each year everyone's age goes up by 1 (of course if you're still alive...) and y-intercept in this case represents their current age.
So the father can be represented as: y=x+38
The sons can be represented as: y = x+13 and y=x+5
The daughter can be represented as: y=x+8
So adding up all his children you get:
(x+13)+(x+5)+(x+8)
This gives you the equation:
3x+26
Now set this equal to the father's age to solve for x (in this context it's years)
3x+26=x+38
Subtract from both sides
2x+26=38
Subtract 26 from both sides
2x=12
Divide both sides by 2
x=6
So in 6 years the father will be the same age as his children put together

Thickness of the book is ~
Refer to the attachment for solution ~
Answer:
Given: Point C is the center of circle.
To Find: ∠ A CB
Solution: Measure of arc A DB=312°
Angle made by complete circle=360°
⇒∠A DB + ∠ AC B= 360°[Total measure of complete circle]
⇒ 312° + ∠ AC B= 360°
⇒∠ AC B = 360° - 312°
⇒ ∠ AC B=48°
45% of what number is 27
0.45x = 27
x = 27 / 0.45
x = 60 <== 45% of 60 = 27