Because 2△+2☆= 10+○.

2☆+3△= 1 1+○

Delta = ( 1)

Because ☆ = 3+02 ☆+3 △ (△ =1) =1+0, that is, 2 ☆ = 8+0.

Get ☆=(7)

Replace ☆ = (7) with ☆ = 3+☆.

Available○ = (4)