I’m not sure which of these you meant to type so I answered both ways
B=(RT-4)/6 multiply by 6
6B= RT-4. Add 4
6B+4= RT. Divide by R
(6B+4)/R = T
Or B=RT -4/6. Multiply by 6
6B=6RT -4. Add 4
6B+4= 6RT. Divide by 6R
(6B-4)/6R = T. Reduce
(3B-2)/3R = T
The inequality is -12x + 3y > 9.
PART A:
The sytem has no solution if inequality does not share a common area. The inequality -12x + 3y > 9 consist the region to left of line -12x + 3y = 9. So for no solution the region to left of equation -12x + 3y = 9 is suitable.
Thus inequality for no solution is, -12x + 3y < 9.
PART B:
For infinite solution the region of both inequality must overlap each other, or the inequality is same with some multiplication of divison factor. So inequality for infinite many solutions is,

Thus inequality for infinite many solution is 12x - 3y < -9.
PEMDAS.
Parentheses
Exponents
Multiplication
Division
Addition
Subtraction
Lets apply that here.
72-[(3x2^3)+48]
So first we start with (3x2^3)
2^3=8
3*8=24
now we do 24+48 which equals 72
now we have 72-72 which equals zero.
So
72-[(3x2^3)+48] = 0
It is the last equation. You square both sides.