Answer:
See below
Explanation:
If what you wrote is (4y²)(5x):
Multiply the coefficients (4·5) and then the variables. Answer is 20xy².
If what you wrote is (4y)²(5x):
1. Square the 4 and the y = 16y²
2. Multiply the coefficients (16·5) and then the variables. Answer is 80xy².