you can use the number sentence 42/7
First write nine ten thousands in standard form which is 90,000. Next divide 90,000 by 10 and you should get 9,000 by crossing out one zero in both numbers. To get 9,000 in unit form all you have to write is 9 thousands. And your answer is 9 thousands
The correct answer is C. 5, 6, -7
$40% 0f 20 is 8
40% × 20 = (40/100) × 20 = 8
S=2LW+2LH+2WH
First, subtract 2LH from both sides
S-2LH=2LW+2LH-2LH+2WH
S-2LH=2LW+2WH
Separate out the W
S-2LH=W(2L+2H)
Divide by 2L+2H to get W alone

Hope this helps.