Answer:
x=12
Step-by-step explanation:
the two inside numbers= the outside, so it would be 7x+21=9x-3. and i would guess that you know it from there. but u would subtract 21 from both sides and then subtract 9x from each side which gives u -2x=-24 and the division cancles the negitive giving u 12. i kindly ask for briainliest :)
