-8
a is equal to 4
-13
5
basically you asked what -28+21 which equals -7
it can't equal 550....i think it equals 15
13...... 9 plus 5 equals 14...... 14 minus 1 equals 13
13 + 5 = 18
5
No, It equals 10
if u mean +13 - (+8) = 5, then yes
it equals 1 and 5/8 or 13/8
X equals 2 :)