That's the second one,
180 - x = r
Whenever two lines cross we get congruent opposite angles and supplemental adjacent angles, i.e. they add to 180 degrees.
The first one is almost right; we have r+y+z=180 and r+x=180 so x=y+z not quite what was written.
8<-5x+20 is one possible answer. it depends on how they are writing it. you need to do the distributed property.
3x + 6 = 12
First operation was subtraction (subtracting 6 to leave 3x alone)
Second operation was division (Dividing 3 from 3x to isolare x)
3x + 6 = 12
3x + 6 -(6) = 12 - 6
3x = 6
=
3 and 3 cancels out
x = 2
volume = 7*7*2 = 49*2=98
she needs to get 98 cubic feet of sand
1/32 its pretty simple come on man