Question 1126533
Sally is 3 years older than Helen.
s = h + 3
 The product of their ages is 70.
s * h = 70
 How old is Helen?
in the above equation, replace s with (h+3)
(h+3)*h = 70
h^2 + 3h = 70
our old friend, the quadratic equation!!
h^2 + 3h - 70 = 0
You can use the quadratic equation; a=1; b=3; c=-70, but this will factor to
(h+10)(h-7) = 0
I'm sure Helen is a positive person, therefore
h = 7 yrs
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Obviously Sally will be 10, it checks out; 10 * 7 = 70