Explanation:
For all of these problems, we are given the values of the variable x.
Now, we just need to input them into the equations.
1) 5x-100 x=25
 5(25)-100
 125-100= 25
2) x^3 x=4
 4^3= 4×4×4= 64
3) 2x-20 x=5
 2(5)-20
 10-20= -10
4) 7x+25 x=4
 7(4)+25
 28+25= 53
5) x^3+9 x=3
 3^3+9= (3×3×3)+9
 27+9= 36
6) 4(x-5) x=20
 4(20-5)
 20(4)-5(4)
 80-20= 60
7) 6x+y^2 x=4 and y=3
 6(4)+3^2
 24+(3×3)
 24+9= 33
Hope this helps! :)