Question 844047
Plot cost, {{{C}}} on the vertical axis
Plot time in hours, {{{t}}} on the horizontal axis
Use the general point-slope formula
{{{ ( C - 2700 ) / ( t - 3 ) = ( 3100 - 2700 ) /  ( 5 - 3 ) }}}
{{{ ( C - 2700 ) / ( t - 3 ) = 400 /  2 }}}
{{{ ( C - 2700 ) / ( t - 3 ) = 200 }}}
{{{ C - 2700 = 200*( t - 3 ) }}}
{{{ C - 2700 = 200t - 600 }}}
{{{ C = 200t + 2100 }}}
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If {{{ t = 1.5 }}},
{{{ C = 200*1.5 + 2100 }}}
{{{ C = 2400 }}} naira
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Check the equation:
{{{ C = 200t + 2100 }}}
( 5, 3100 )
{{{ 3100 = 200*5 + 2100 }}}
{{{ 3100 = 1000 + 2100 }}}
{{{ 3100 = 3100 }}}
OK
You can check ( 2700, 3 )