Question 287596
Let x=Hannah's age
y=Mark's age
z=Tom's age
x+y+z=68--------------------eq1
y-z=difference between Mark and Tom's age
x=2(y-z)--------------------------eq2
y+z=16x---------------------------------eq3

From eq 1, y+z=68-x----substitute this for y+z in eq3
68-x=16x  add x to each side
17x=68
x=4--------------------------Hannah's age
Substitute x=4 into eq2
4=2y-2z or
y-z=2----eq2a
substitute x=4 into eq3
y+z=64-----eq3a
add eq 2a and eq 3a
2y=66
y=33---------------------- Mark's age
substitute y=33 into eq3a
33+z=64
z=31-----------------------------Tom's age

CK
Difference between Mark and Tom's age =33-31=2; Hannah is twice that old OK

Mark and Tom's combined age 33+31=64 is 16 times Hannah's age OK

Hope this helps--ptaylor