Answer:
7) refer to d=rt triangle so answer is t= d/r
8) rearrange by dividing so it should be PV/nR = T
9) move 5r to other side which become 2p = q - 5r then divide by 2. final answer is p = q-5r/2
10) multiply both side by b/1 so b got cancel on left side
right side become c(b/1) which is same as cb
then you divide both side by c to isolate b on the right side
final answer is a/c=b
