Answer:
50/21 or 2.38
Explanation:
3.5 = (D/2) + (D/40) + 2.25
Make D/2 and D/40 have a common denominator of 40.
D/2(20/20) = 20D/40
New equation:
3.5 = 20D/40 + D/40 + 2.25
Combine like terms:
3.5 = (20D/40 + D/40) + 2.25
3.5 = 21D/40 + 2.25
The first step to isolating a variable is subtracting constants from both sides:
3.5 = 21D/40 + 2.25
-2.25 -2.25
3.5 - 2.25 = 21D/40
1.25 = 21D/40
Let's get rid of 40 by multiplying both sides by 40 since the inverse operation of division is multiplication.
1.25 = 21D/40
· 40 · 40
1.25(40) = 21D
50 = 21D
Now divide both sides by 21 to isolate D since the inverse operation of multiplication is division:
50 = 21D
/21 /21
D = 50/21
If you want to keep this number in a fraction in simplest form, it already is in simplest form but if you want it in decimals, (because it doesn't divide perfectly) it would be:
D = 2.38095238095
Rounded to nearest hundredth:
D = 2.38
So, your answer is 50/21 or 2.38.