First thing you need to do, in order to add straight across like this: [tex] \frac{13}{20} + \frac{5}{8} [/tex] You need to set the denominators equal to each other, by finding out the greatest common multiple. Which in this case is 40.
[tex] \frac{2 \times 13}{2 \times 20} + \frac{5 \times 5}{5 \times 8} [/tex] When you multiply, whatever you do to the denominators you must do the same to the numerator. Our new fractions should now have equal denominators like below: [tex] \frac{26}{40} + \frac{25}{40} [/tex] Now keeping the same denominators you can simply add together 26 and 25 [tex]26 + 25 = 41[/tex] [tex] \frac{41}{40} [/tex] Now you need to simply this improper fraction, to get the final answer.
