Answer:
Brock completed approximately 38 pull ups in the initial stage of training.
Step-by-step explanation:
We are given the following information in the question:
Ration of pull ups and box jumps initially =
[tex]\displaystyle\frac{5}{4}[/tex]
Ration of pull ups and box jumps later =
[tex]\displaystyle\frac{2}{7}[/tex]
Number of box jumps completed in the end of training = 53
Total number of exercises done in the end = 2x + 7x = 9x
We use the concept of ratio.
[tex]7x = 53\\\\=x = \displaystyle\frac{53}{7}\\\\\Rightarrow 2x = \frac{106}{7}\\\\\Rightarrow \text{Total number of excercise} = \frac{477}{7}[/tex]
Initially,
Total number of exercise = 5y + 4y
[tex]9y = \displaystyle\frac{477}{7}\\\\\Rightarrow y = \frac{477}{63}\\\\\Rightarrow \text{Pull ups done initially} = 5y = 5\times \frac{477}{63} = 37.85 \approx 38[/tex]
Thus, he completed approximately 38 pull ups in the initial stage of training.