The first box has a total of 10 items ( 3 pencils + 7 pens = 10)
The probability of picking a pen would be 7/10
The second box has a total of 8 items ( 4 pencils + 4 crayons = 8)
The probability of picking a crayon would be 4/18, which reduces to 1/2
To find the probability of doing both, multiply each probability together:
7/10 x 1/2 = 7/20
The probability is 7/20