Question 964106
.
L=Lauren's age; D=David's age=L-4
{{{LD=45}}} Substitute for D
{{{L(L-4)=45}}}
{{{L^2-4L=45}}} Subtract 45 from each side.
{{{L^2-4L-45=0}}}
{{{(L-9)(L+5)=0}}}
{{{L-9=0}}} {{{or}}} {{{L+5=0}}}
{{{L=9}}} {{{or}}} {{{L=-5}}}
ANSWER: Lauren is 9 years old.
CHECK:
D=L-4=9-4=5 David is 5 years old.
L*D=45
9*5=45
45=45