Question 878143
If all the vehicles were cars, the amount 
would be {{{ 31*4 = 124 }}}
If one of the vehicles was a truck,
{{{ 30*4 + 1*7 = 127 }}}
If 2 were trucks,
{{{ 29*4 + 2*7 = 130 }}}
If 3 were trucks
{{{ 28*4 + 3*7 = 133 }}}
If 4 were trucks
{{{ 27*4 + 4*7 = 136 }}}
If 5 were trucks
{{{ 26*4 + 5*7 = 139 }}}
If 6 were trucks 
{{{ 25*4 + 6*7 = 142 }}}
If If 7 were trucks
{{{ 24*4 + 7*7 = 145 }}}
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Someone had to have either added some money
or taken some money for the total to be $140