Spenda has the right idea - take the next step and try to work these odd calculation things out yourself.

Let me help with this one.

First, let's agree how many outs you have. We'll call it 15. He might have the same straight you're drawing to (thinking of the low straight if the 8 comes) and he might be holding two diamonds with the A for a better flush than you - but then he might be bluffing and your overcards be outs also. In many cases like this you weigh these two sets of factors:
More outs: Already ahead (bluff), overcards
Less outs: Some outs give split outs, some outs are held by opponent, some outs are outs that improve us but improve our opponent also to a better hand.

Often, for simplicity people suggest that the outs for straights and flushes are about exact when all of the above is counted in. In the present case I think it's highly likely that your opponent is holding an 8, which means there are 2 and not 3 outs that are 8, and those 2 are to split pots. So maybe 13 or so is a truer number.

Anyway, in this way you decide on a number of outs that we can call good, which you will base your calculations on. Let's call it 15 for simplicity.

The rule of 2 and 4 says that 15 outs with one card to come means you have a 30% chance of hitting one of your outs.

The pot contains $1.18 and the bet is $1.74. Assuming you call, you will be calling $1.74 to win $2.92. Your call will make a total pot of $4.68. If you win 1.74 / 4.68 of the time - 37% of the time - or more you would be correct to call.

As an example, if he bets exactly the size of the pot you need to win 33.3% of the time.

The above is using equity. You can do the same with pot odds.

You have yet to see one of the last 46 cards - 15 are good, and 31 are bad - that's odds slightly higher than 2 to 1 against you winning. The odds offered by the pot are 2.92 to 1.74. 2.92 divided by 1.74 is 1, with a rest of 1.18 which is happens to be exactly two thirds of 1.74 - so the pot odds are 1.66 to 1 - worse than the odds against you winning.