Instead of drawing the model, we can work with the ratios too.
The ratio of Jack’s mass to Peter’s mass is 7 to 6.
And, Peter’s mass is two-thirds of Dan’s mass
which means the ratio of Peter’s mass to Dan’s mass is 2 to 3.
Peter’s mass is the common quantity in both ratios.
So, let’s make the number of units representing Peter’s mass in both ratios the same.
To do this, we
multiply both numbers in the second ratio by 3.
This gives us 6
to 9.
With these two ratios, we can find the answers for the three parts in the same way as we did using the model.