Question 485285
total charge of company a in t hours is {{{(80+55t)}}}
total charge of company b in t hours is {{{75t}}}
For what lengths of time in moving company b more expensive than moving company a? , So total charge of company a in t hours<total charge of company b in t hours
{{{80+55t<75t}}}
{{{55t-75t<-80}}}
{{{-20t<-80}}}divide by (-20), when we divide inequality by negative number the sign of inequality are changed 
{{{t>80/20}}}
{{{t>4}}}
If working time is {{{t>4}}}hours, then  moving company b more expensive than moving company a