Question 1072046
train a and train b, weigh a total of  tons.
HOW MANY?  Some unknown, ungiven number, T.


{{{system(a+b=T,a-b=60)}}}



{{{2a=T+60}}}
{{{highlight_green(a=(T+60)/2)}}}


{{{2b=T-60}}}
{{{highlight_green(b=(T-60)/2)}}}