Answer:
a = 17
Step-by-step explanation:
a + (-5) = 12
Open the bracket;
a - 5 = 12
Add 5 to both sides
a - 5 + 5 = 12 + 5
Therefore,
a=17
any number plus a negative number is basically subtracting the absolute value of the negative number. so 12 + 5 = 17
