4. find the solution to each equation mentally.
a. 30+ a = 40
b. 500+ b = 200
c. -1+c= -2
d. d +3,567 = 0

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A, 10. b,-300. c, -1. d, -3567.
youre basically looking for the number that gets you to the other number. how far away from 30 is 40? 10. how far is 500 from 200? 300, but in the other direction so its negative. and for D since the final number is 0 just use the same number but flip the sign

Step-by-step explanation:

a. 30+ 10= 40              a= 10

b. 500+ (-300) = 200           b= -300

c. -1 + (-1) = -2              c= -1

SORRY IDK THE LAST ONE

30 is the answer
i can help if need be