Answer:
(a) The breaking strength is 10 times the number of layers;
(b) 35 pennies; (c) 80 pennies.
Explanation:
(a) The graph
I plotted the graph in the diagram below. It looks roughly the same as yours.
It looks like the breaking strength goes up another 10 pennies each time you add a layer.
Saying it another way, the breaking strength is 10 times the number of layers.
(b) Breaking strength of 3.5 layers.
The breaking strength is 10 times the number of layers.
If we have 3.5 layers, the breaking strength should be
10 × 3.5 = 35 pennies
See the red point labelled B on the graph.
(c) Breaking strength of eight layers.
The breaking strength is 10 times the number of layers.
If we have 8 layers, the breaking strength should be
10 × 8 = 80 pennies
See the orange point labelled C on the graph.