amy has three pencil cases. In her hearts pencil case, she has seven black pens and three red pens. In her furry pencil case, she has six black pens and four red pens. In her new moon pencil case, she has five black pens and five blue pens.
Amy takes, at random, one pen from each pencil case.
Work out the probability that she takes exactly one black pen.

please help!

Ok, so what have you worked out so far?

sounds like probability, draw it out first or use a table

... Black Red total... Chance
Heart... 7... 3... 10... 7/10
furry
moon

Now what is the chance of finding a black pen in each of these bags compared to the total amount of pens in that bag?

amy has three pencil cases. In her
hearts pencil case, she has seven black pens and three red pens. In her
furry pencil case, she has six black pens and four red pens. In her new
moon pencil case, she has five black pens and five blue pens.
Amy takes, at random, one pen from each pencil case.
Work out the probability that she takes exactly one black pen.

please help!