what is the lengths of all 3?

Answer:
AB=15
AC=15 as an isosceles triangle base arm
BC=4
Step-by-step explanation:
TO find value of (X)
take bath base arm
2x-1=X+7
2x-x=7+1
X=8
now
put value of (X)
AB= X+7= 8+7=15
AC=15 as an isosceles triangle base arm because both arm should be equal
AC=2X-1=2*8-1=15
BC= X-4=8-4=4
it may help you(: