Final answer:
Brad had 50 marbles and 70% of them were green, which means he had 35 green marbles.
Step-by-step explanation:
To calculate how many of Brad's marbles were green, we need to find 70% of 50. To do this, you multiply 50 marbles by 0.70 (which represents 70%). So, the calculation is as follows:
50 marbles × 0.70 = 35 green marbles.
Therefore, Brad has 35 green marbles.