A father is 4 times as old as his son. In 20 years the father will be twice as old as his son.. Find their present ages

x = the age of his son now, then the age of the father is 4x.

In 20 years,

son's age = x + 20

father's age = 4x + 20

solve the equation for x:

4x + 20 = 2(x + 20)

4x + 20 = 2x + 40

2x = 20

x = 10

So the age of his son now is 10, and the age of the the father now is 40.

13

step-by-step explanation:

169-1=168

168-3=165

165-5=160

160-7=153

153-9=144

144-11=133

133-13=120

120-15=105

105-17=88

88-19=69

69-21=48

48-23=25

25-25=0

since it took 13times to completely subtract it hence its square root is 13

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