Hello!
The answers are:
1
![x=-9](https://img.qammunity.org/2020/formulas/mathematics/high-school/hkafqts9aib3p0otn5eljcdb9e3d2i1j10.png)
2
![x=16](https://img.qammunity.org/2020/formulas/mathematics/high-school/54vswjfry49nj26yghmmk853abj0561j72.png)
3
![r=-2](https://img.qammunity.org/2020/formulas/mathematics/high-school/2dkkdxcmsdkypdc6w1ic2ebv6xu1xafyju.png)
Why?
To know the solution of the problems, we need to isolate each variable.
Remember that:
- If we have an equality: if the number is adding (positive sign), and if you need to move it to the other side of the equality, its sign changes to negative.
- If we have an equality: if the number is subtracting (negative sign), and if you need to move it to the other side of the equality, its sign changes to positive.
- If we have an equality: if the number is part of a product , and if you need to move it to the other side of the equality, the same number will be dividing the factors of the side.
So:
1 - Solving for x
![-3x+4=31\\-3x=31-4\\-3x=27\\x=(27)/(-3)=-9](https://img.qammunity.org/2020/formulas/mathematics/middle-school/cwpw6m6ewp2gael27gqhoiwsd2qsaoxrd1.png)
2 - Solving for x
![2x-10=22\\2x=22+10\\2x=32\\x=(32)/(2)=16](https://img.qammunity.org/2020/formulas/mathematics/middle-school/apto5twphctmn64edt268p6m8m7qwwnh71.png)
3 - Solving for r
![40=32-4r\\4r=32-40\\4r=-8\\r=(-8)/(4)=-2](https://img.qammunity.org/2020/formulas/mathematics/middle-school/v1l9ty6j30g6bk9glr1qclzf8l4nwyo6rv.png)
Have a nice day!