1) In order to add or subtract fractions denominator must be equal
[tex] \frac{1}{4} + \frac{2}{5} [/tex]
Lcm of denominator is 4×5=20 since they are co primes
[tex] \frac{1}{4} \times \frac{5}{5} + \frac{2}{5} \times \frac{4}{4} [/tex]
Now the denominator becomes same
[tex] \frac{5 + 8}{20 } = \frac{13}{20} [/tex]
2)
[tex] \frac{3}{8} - \frac{1}{2} [/tex]
Lcm =8
[tex] \frac{3}{8} \times \frac{1}{1} - \frac{1}{2} \times \frac{4}{4} [/tex]
[tex] \frac{3 - 4}{8} = \frac{ - 1}{8} [/tex]
3)
We just need to add the fractions
[tex] \frac{1}{4} + \frac{1}{3} [/tex]
Lcm=12
[tex] \frac{1}{4} \times \frac{3}{3} + \frac{1}{3} \times \frac{4}{4} [/tex]
[tex] \frac{3 + 4}{12} = \frac{7}{12} [/tex]
hope it helps :)
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