first, multiply each side by 5 to eliminate it.
a-3/5=-7/10
a-3=35/10
now add 3
a= 35/10 +3 or 65/10 or 6.5
second question: 2/3+r=-4/9
subtract 2/3 from each side
r=-4/9-2/3 you need a least common demonator (pretty sure i spelled that wrong)
-4/9-2/3= - 4/9 -6/9 (9 is least common deminator, 9 goes into 9 1 time, 1x 4 is 4 and 9 goes into 3 3 times, 3x2 is 6) now your ready to subtract an easier way is to make it addition and change the signs so:
-4/9+ (-2/3) = -4/9+(-6/9) = -10/9 is your answer