Verified Answer :

\(a + 3(5a+8) = 72\)
First you want to multiple 3(5a+8):
\(a + (15a + 24) = 72\)
Next, add a + 15a:
\(16a + 24) = 72\)
Then, subtract 24 from both sides:
\(16a = 48\)
Finally, divide both sides by 16:
\(a = 3\)

you would look at pemdas or order of operations
after () you would do multiplication so
a+3(5a+8)=72
first you do 3 times (5a+8) and use the distrubtive property
a+15a+24=72
so add like terms
16a+24=72
subtract 24 from both sides
16a=48
divide both sides by 16
a=3