Answer:
Not enough tables.
Explanation:
Circumference is 2*pi*r
The diameter is 2 times the radius or 2r, if the table diameter is 180cm. All we need to do is multiply by pi (3.14159) to get the circumference.
180*pi = 556.48cm
If each guest needs 70cm then we divide the circumference by 70
556.48/70 = 8.08 but we cant have a portion of a person so we can fit 8 people per table.
18 tables with 8 at a table is 8 x 18 = 144
If 145 guests are attending then there aren't enough tables, you are 1 table short.