Consonant blends (also called consonant clusters) are groups of two or three consonants in words that makes a distinct consonant sound, such as "bl" or "spl." Consonant digraphs include bl, br, ch, ck, cl, cr, dr, fl, fr, gh, gl, gr, ng, ph, pl, pr, qu, sc, sh, sk, sl, sm, sn, sp, st, sw, th, tr, tw, wh, wr.
That is, add the first number with the second number with its sign changed. For simple numbers, it does not make much difference, but for algebraic expressions, it can help a lot.
To subtract both binomials, we write the first plus the second with changed signs:
