Answer:
c=13 and a=20
Step-by-step explanation:
Here you need to use the Pythagoras theorem :
c²=a² + b²
c = √a² + b²
c = √(12)²+(5)²
c= √144+25
c = √169
c = 13
2) c²=a²+b²
b= √c²-b²
b= √(29)²-(21)²
b = √400
b = 20
In 2 you change your formula just so that it can be easier and just calculate your length straight forward but you can also just do it in the original equation
80
1st row 5 -7 -1
2nd row -2 4 -5
3rd row -6 0 3