whats the answer

http://www.cymath.com/answer.php?q=7%2F8%2B3%2F5

${7 \over8}+{3 \over5}=x$

LCM

${35 \over40}+{24 \over40}=x$

Add the NUMERATORS ONLY

$x={54 \over40}$

Simplify

$x=1{14\over40}$

Simplify

$x = 1{7\over20}$

Here's another method  -  useful when the denominators have no factors in common....like this one....

7/8   +  3/5             

Cross-multiply the 7 and 5   = 35

Cross multiply the 5 and 8   = 40

Write these,in order, with the same sign (a plus) between them as in the original problem.....so we have

35 +  40  

Add these  = 59   (1)

Multiply the original denominators  = 8 * 5   = 40    (2)

Put   (1)  over (2)   =

59 / 40