Punnett Square is perfect for these types of probability questions!
Punnett Square is one box divided into four equal boxes where we put the letters of allele on top of the box. An example is attached.
Given this question: E is energetic, e is lazy
We need to know that: homozygous means same alleles (EE or ee) , heterozygous means different alleles (Ee)
Dominant means EE or Ee, and recessive is ee.
Reading the question, we can conclude that the cross is ee x Ee:
E e
e Ee ee
e Ee ee
The question is asking how much of the predicted offspring will be ee.
The answer is 50% (2/4)