Help me :( it's algebra and I am so confused. (explanation would be nice)

Answer:
- 3[tex]x^{4}[/tex] + 15x² - 3x
Step-by-step explanation:
Given
(5[tex]x^{4}[/tex] - 3x + 8x²) - (8[tex]x^{4}[/tex] - 7x²)
Remove the parenthesis on first and distribute second by - 1
= 5[tex]x^{4}[/tex] - 3x + 8x² - 8[tex]x^{4}[/tex] + 7x² ← collect like terms
= - 3[tex]x^{4}[/tex] + 15x² - 3x ← in standard form