Question 511508
Think of an x-y plot where x is the years passed
and y is the salary
I can say when
{{{ S = 60 }}} ( salary in thousands)
{{{ t = 0 }}}
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when
{{{ S = 70.5 }}}
{{{ t = 3 }}}
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I can write the equation in point-slope form
{{{ ( S - 60 ) / ( t - 0 ) = (70.5 - 60 ) / (3 - 0 ) }}}
{{{ ( S - 60 ) / t = 10.5 / 3 }}}
multiply both sides by {{{ 3t }}}
{{{ 3*( S - 60 ) = 10.5t }}}
{{{ 3S - 180 = 10.5t }}}
{{{ 3S = 10.5t + 180 }}}
{{{ S = 3.5t + 60 }}}
check:
When {{{ t=0 }}}, he makes $60 thousand -OK
When {{{ t = 3 }}}, he makes {{{ 3.5*3 + 60 = 70.5 }}} thousand -OK
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The slope is how fast his salary is increasing
The S-intercept is his starting salary
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After 12 years,
{{{ S = 3.5*12 + 60 }}}
{{{ S = 42 + 60 }}}
{{{ S = 102 }}} 
He will make $102,000 after 12 years