Answer :
So I worked out the height and realised that it was 45 so yeah... Anyway... Here's your answer: 48*45/2=1080 so the area of 1 triangle is 1080cm^2.
1080*7=7560 7560*12=90720 so he needs 90720cm^2 to make 7 dozen signs.
1080*7=7560 7560*12=90720 so he needs 90720cm^2 to make 7 dozen signs.