Barbara is a waitress and she usually takes between 5 and 9 tables at a time. she found that when she is assigned five tables, she averages $20 in tips per table per shift. if she is assigned more tables, the amount of attention she gives to each table decreases. therefore, she averages less in tips per table. suppose each additional table causes every table to bring in $3 less in tips. which of the following equations could be used to find the amount of money she would make in tips if she takes 5 + x tables?