When did Spencer Silver discover the formula for the “unglue”?

Several years before Fry had his idea .

Explanation:

The Evolution of Useful Things by Henry Petroski deals with the issues of small trivial things and how they came to be. These small details may seem trivial but in actuality, they play a huge part in our lives. Petroski delves into the details of these things and how they have a huge impact on our lives.

Spencer Silver was a 3M researcher who had come upon the formula for the "unglue" while working "in the course of developing very strong and very tacky adhesives". This was several years earlier, before Art Fry, a chemical engineer who came upon the idea in 1974.  

brainliest please

hi my name is bob.hi and bye and this this tahta jjsab jjja

sentences vary by structure as well as by function. there are compound, complex, and compound-complex sentences.

simple sentence

i like to read.

a simple sentence has one independent clause.

compound sentence

i like to read, and i also like to write.

a compound sentence includes more than one independent clause, connected by a coordinating conjunction (and, but, for, nor, or, so, or yet).

complex sentence

i prefer to read books that are bestsellers.

a complex sentence includes one independent clause and one or more dependent clauses. (a dependent clause is one that cannot stand alone.) types of dependent clauses include relative clauses (i kicked the boy who pinched me), adverb clauses (i am going home now because i have a curfew), and noun clauses (i don't know what to do next).

compound-complex sentence

although i prefer to read current bestsellers, i do like to read old agatha christie mysteries, and i also like some 20th-century science fiction.

compound-complex sentences take a bunch of clauses (multiple independent clauses, and one or more dependent clauses) and toss them together like a salad. although these sentences take practice to write in a grammatically correct fashion, they can hold a tremendous amount of meaning, and are common in academic writing.