Super girl had -4.5 rad. She uses her strength to get 7.1 more rads
-4.5 + 7.1 = 2.6
2.6 is final amount of radiation.
Poison Ivy has $17.34. She writes a check for 24.86
17.34 - 24.86 = - 7.52
Poison Ivy has $ -7.52 for her account balance
hope this helps