Answer:
The friends will each have passed _33_ scales in _7_ weeks.
Explanation:
We must write an equation for the number of scales that Nick approves and an equation for the number of scales that Mary approves.
For Nick we have:
5 initial scales
Nick has committed to approve 4 scales per week. Let's call x the number of weeks.
So the number of scales and for Nick is:
![y = 5 + 4x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/v09awa4xwpgoce8cvxksk7ud3pa3p2i8p0.png)
For Mary we have:
12 initial scales
Mary has committed to approve 3 scales per week. Let's call x the number of weeks.
So the number of scales and for Mary is:
![y = 12 + 3x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/fpuhh9h6wgm1rj5hw9wt6udwp55txa9re2.png)
To know when the two friends have passed the same number of scales we must equal both equations and solve for x:
![12 + 3x = 5 + 4x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/fiihskazv4t8q2bqxkiv2m17dpx73xpaoj.png)
![12-5= 4x-3x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3nr7tg6h4ljtzk7mup32tlx03zomnn8cpo.png)
![x= 7\ weeks](https://img.qammunity.org/2020/formulas/mathematics/middle-school/tk1sswf09vx0yqoftl10f210jjgde5hdwg.png)
And
![y=12+3*7\\\\y=33\ scales](https://img.qammunity.org/2020/formulas/mathematics/middle-school/oi07r6i1zf06818wvupkew234xcn3ebyzr.png)