She use 17 1 4 cups of sugar and needs another 7 8 cups for other batch how many cups will she use alltogether

What you want to do is find the greatest common denominator, so for now put the 17 to the side and focus on the 1/4 and 7/8, we can find the GCD (greatest common denominator) by multiplying 1/4 • 8/8 = 8/32 And then multiplying 7/8 • 4/4 = 28/ 32 So here we have remaining 17 & 8/32 cups PLUS 28/32 cups, you can add the numerators straight across and keeps the denominators the same, which says that she uses 18 & 4/32
Simplified version: 18 & 1/8