Answer:
<em>75</em>
Step-by-step explanation:
Subtracting a number means adding the opposite.
The opposite of a number is the number you obtain by just changing the sign.
The opposite of 5 is -5. The opposite of 100 is -100. The opposite of -4.5 is 4.5. The opposite of 0 is 0. Zero is the only number that is equal to its opposite.
You need to subtract -45, so add the opposite of -45 which is 45.
30 - (-45) = 30 + 45 = 75
