Use the permutation formula to solve a problem when n = 8 and r = 4. A. 420
B. 1,680
C. 6,720
D. 26,880

Astudent simplified a rational expression as shown.

Simplify the expression. -2/5(10+15m-20n)

Girardo is using the model below to solve the equation . girardo uses the following steps: step 1 add 4 negative x-tiles to both sides step 2 add 1 negative unit tile to both sides step 3 the solution is which step could be adjusted so that gerardo's final step results in a positive x-value? in step 1, he should have added 4 positive x-tiles to both sides. in step 1, he should have added 3 negative x-tiles to both sides. in step 2, he should have added 4 negative unit tiles to both sides. in step 2, he should have added 1 positive unit tile to both sides.