Question 356774
Let T be the number of tomatoes, L the number of lettuce heads.
{{{T+L=12}}}
{{{T=2*L}}}
Substitute,
{{{2L+L=12}}}
{{{3L=12}}}
{{{L=4}}}
Then,
{{{T=2(4)=8}}}
She bought 8 tomatoes and 4 lettuce heads.