Differentiation...

_ab_caa_bbcaa_b_caaa

If the area of the triangle formed by $$ (-2,5), (x,-3) $$ and $$(3,2)$$ is $$14 $$ square units, then $$x=$$ ____.

ab _ bc _ c _ ba _ c

If CAT is $$48$$,  Z is $$52$$ Then what  is TEA equal to ?

A group of 1200 persons consisting of captains and soldiers is travelling in a train. For every 15 soldiers there is one captain. The number of captains in the group is: 

Observe the following pattern for obtaining the sums then find the sum of numbers from 781 to 790?
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55
11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20 = 155
21 + 22 + 23 + 24 + 25 + 26 + 27 + 28 + 29 + 30 = 255
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
51 + 52 + 53 + 54 + 55 + 56 + 57 + 58 + 59 + 60 = 555
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
101 + 102 + 103 + 104 + 105 + 106 + 107 + 108 + 109 + 110 = 1055
251 + 252 + 253 + 254 + 255 + 256 + 257
258 + 259 + 260 = 2555

A, B, C and D are four 4-digit numbers each having the digit 9 only once and in the place shown None of the other digits are known
What can be said about A, B, C and D?

At the end of a business conference, the ten people present all shake hands with each other once. How many handshakes will there be altogether? 

In a chess tournament each of six players will play every other player exactly once. How many matches will be played during the tournament? 

Choose the correct statement(s):