Question 1169107
Dogs between {{{2}}} to {{{13}}} years old, age at an average rate of {{{4}}} human years for every dog year. 


a)

Write the equation in {{{y = mx +b}}} form


{{{y=mx + b }}} where the dogs age is {{{x}}}, and  the dogs age in human-years is {{{y}}}


if given that {{{x=2}}}, then {{{y=2*4=8}}}

{{{8=m*2 + b }}} ......eq.1

if given that {{{x=13}}}, then {{{y=13*4=52}}}

{{{52=m*13 + b }}} ......eq.2

solve this system:

{{{8=2m + b }}} ......eq.1

{{{52=13m + b }}} ......eq.2
_____________________________________ subtract eq.1 from eq.2

{{{52-8=13m-2m + b-b }}}
{{{44=11m }}}
{{{m=44/11 }}}
{{{m=4 }}}

substitute in eq.1 to calculate b

{{{8=2*4 + b }}} ......eq.1
{{{8=8 + b }}}
{{{8-8 = b }}}
{{{ b=0 }}}

your equation is

{{{y=4x  }}} 

b)

What is the age in human-years of a {{{7 }}}year old dog?

{{{x=7}}}

{{{y=4*7  }}}

{{{y=28  }}} ->the age in human-years 


c)

A friend tells you their dog is as old as their {{{60}}} year old grandparents. How old is the dog in dog-years?

{{{y=60}}}

{{{60=4x }}}

{{{60/4=x }}}

{{{x=15 }}}->  their dog is old {{{15}}}