Let x denote the number of model A phones.
Let y denote the number of model B phones.
We can set up two equations with the given information.
The total number of phones in the inventory is 195.
[tex]x+y=195\quad eq.1[/tex]
Model A is valued at $75 and Model B at $110 and the total worth of these phones is $17,215.
[tex]75x+110y=17215\quad eq.2[/tex]
Now we can use the substitution method to find the values of x and y.
From eq. 1, you can separate out any one of the variables and substitute it into eq. 2
[tex]y=195-x\quad eq.1[/tex]
Substitute it into the eq. 2
[tex]\begin{gathered} 75x+110y=17215 \\ 75x+110(195-x)=17215 \\ 75x+21450-110x=17215 \\ 75x-110x=17215-21450 \\ -35x=-4235 \\ 35x=4235 \\ x=\frac{4235}{35} \\ x=121 \end{gathered}[/tex]
Finally, substitute the value of x into eq. 1 to find the value of y.
[tex]\begin{gathered} y=195-x \\ y=195-121 \\ y=74 \end{gathered}[/tex]
Therefore,
x = 121 the number of model A phones
y = 74 the number of model B phones
