The word is NOT "solve".  You can only 'solve' equations.

How to tell if it's an equation or an expression: If it has an equal
sign " = " then it is an equation and you can use the word "solve".  But
if there is no equal sign then you can't use the word "solve".  In your
case the word is "factor" if you live in the US, or if you live in the UK,
the word is "factorise".

5xy+10x+10y+20

Take factor 5 out of the entire expression:

5[xy+2x+2y+4]

Use brackets [] instead of parentheses () so you can insert parentheses

Out of only the first two terms inside the bracket factor out x:

5[x(y+2)+2y+4]

Out of the last two terms inside the bracket factor out +2.

5[x(y+2)+2(y+2)]

Now there are two terms inside the bracket so take (y+2) out of each.

5[(y+2)(x+2)]

Now you can drop the brackets:

5(y+2)(x+2)

Edwin