29/5 should be the correct answer
Answer is in the attachment below. If you have any questions about the workings, just leave a comment below.
The answer is

steps
#1) Try to leave a by itself by dividing any variable next to it

you can only divided these variables as all these variables in the original equation. are being multiplied. The opposite if multiplication is division.
<span>7√7 - 2√28
2 sqrt(28) = 4 * sqrt(7)
7*sqrt(7) - 4*sqrt(7) =
3 * sqrt(7)
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