(1) 5a²b - 6ab³c + 3a⁵ is a fifth degree polynomial. This is because the highest index power is to the power of 5. The third term in the expression is raised to the power of five.
(2) 5a²b - 6ab³c + 3a⁵ has a leading term of 5. This is False. The leading term has the highest power of an unknown. a raised to the power of 5 makes the number 3, the leading term. So the leading term is 3
(3) 5a²b - 6ab³c + 3a⁵ contains three terms. This is also correct because the addition and subtraction signs effectively separates the terms in the expression, and they are 5a²b, 6ab³c and 3a⁵.
(4) 12x - 10x⁵ - 7 + 3x⁴ is equivalent to -10x⁵ + 3x⁴ + 12x - 7. This is True because the numbers have all swapped positions but the signs in front of each expression remains unchanged and hence the value of both the one on the left and that on the right would be exactly the same.
(5) 12x - 10x⁵ - 7 + 3x⁴ has a leading term of -10x⁵. This is true because as explained in number two above, the leading term is that term which has the highest index power (in this case its -10x)
(6) 12x - 10x⁵ - 7 + 3x⁴ has a leading coefficient of 12. This is False because the leading term also contains the leading coefficient, hence the leading coefficient is -10