How do I solve this 3 1/8 - 2 3/20?

calculator?

or turn them into fractions: 25/8 - 43/20

then find a common base (40)

125/40 - 86/40 = 39/40

= 3 1/8 - 2 3/20
= 25/8 - 43/20
= 125/40 - 86/40
= 39/40

Answer: 39/40

Checking back to 3 1/8:
= 39/40 + 2 3/20
= 39/40 + 43/20
= 39/40 + 86/40
= 125/40 or (125/5)/(40/5) or 25/8 or 3 1/8

First, let's find the L.C.M of the denominators 8 and 20

Multiples:

8: 8, 16, 24, 32, 40
20: 20, 40, 60, 80, 100

As you notice, 40 is the least multiple that appears both in 8 and 20 and is therefore the L.C.M.

Now let's solve:

3 1/8 - 2 3/20

= 25/8 - 43/20

= (125 - 86) / 40

= 39/40

Hope this helps.

Find the least common multiple:
..8 = 2 x 2 x 2
20 = 2 x 2 ......x 5
------------------------------------------
........2 x 2 x 2 x 5
= 40

3 1/8 - 2 3/20
= 3 (1 x 5)/(8 x 5) - 2 (3 x 2)/(20 x 2)
= 3 5/40 - 2 6/40
= (3 - 2) + (5/40 - 6/40)
= 1 + (-1/40)
= 1 - 1/40
= 40/40 - 1/40
= 39/40

convert mixed fraction to simple fraction:
3 1/8 = (8x3+1)/8 = 25/8
2 3/20 = (20x2+3) = 43/20
therefore the given question will be:

= 25/8 - 43/20
take LCM of the denominators (i hope u know how) it is 40

= [(25x40/8) - (43x20/40)] / 40
= [125 - 86]/40
= [39]/40
= 39/40
in decimal: 0.975

3 + 5/40 - 2 - 6/40

1 + 5/40 - 6/40

45/40 - 6/40

39/40

3 1/8 - 2 3/20

25/8 - 43/20
125/40 - 86/40 = x
39/40 = x