For the first expression, we have 1.4², this can be expressed as 1.4×1.4 and then we get:

For the second expression, 300 ÷ 2(0.5 + 4.5)² we must start by solving the sum inside the parenthesis, then we get:
300 ÷ 2(0.5 + 4.5)² = 300 ÷ 2(5)²
Then, solve the exponent on the right of the division symbol:
300 ÷ 2(5)² = 300 ÷ 2×25
Now, solve the multiplication
300 ÷ 2×25 = 300 ÷ 50
Now, we can solve the division
300 ÷ 50 = 6
Then, 300 ÷ 2(0.5 + 4.5)² = 6
For the last expression, we must start with the exponent:

Now we can solve the multiplication:

In order to divide one fraction by another one we just have to keep the first fraction unchanged, change the ÷ for a × and flip the second fraction, like this:

Then, the value of the last expression is 4/3