Question 950742
A = Alice's age     B = Bob's age


Start out by writing 2 equations that match the information given. 


Alice's age = Bob's age + 8 years
{{{A=8+B}}}


Bob's age times 2 = Alice's age in 3 years
Alice's age in 3 years is the same as her age + 3 years
{{{2B=A+3}}}


Plug The first equation into the second equation using the substitution method.
{{{A=8+B}}} plug in {{{8+B}}} into the second equation where there is an {{{A}}}.


{{{2B=A+3}}}
{{{2B=(8+B)+3}}}


solve for B


{{{2B=B+11}}}
{{{B=11}}}


Bob's current age is 11.