Answer:
for every new hexagon, you just add 5 toothpicks, that's even true for the first one, if we lay down one starter toothpick before the first step
then we can write it as s formula:
t(x) = 1 + 5x
wich gives us the required number of toothpicks by plugging in the desired ammount of hexagons (x)
2.
t(5) = 1 + 5*5 = 25
3.
t(12) = 1 + 5*12 = 61
4.
76 = 1 + 5*x
75 = 5x
15 = x
he can build 15 hexagons
5.
101 = 1 + 5x
100 = 5x
20 = x
he can build 20 hexagons
hope it helps. have a great day