Question 113980
LET X BE THE SIDES OF THE ISOSCELES TRIANGLE.
THE BASE IS (X-1).
PERIMETER=2*SIDES+BASE
20=2X+(X-1)
20=3X-1
3X=20+1
3X=21
X=7 FOR THE LENGTH OF THE SIDES.
THUS THE BASE=7-1=6
PROOF:
20=2*7+(7-1)
20=14+6
20=20