<p>how??</p>
<p>well first of all choice c implies choice b and they can’t both be correct. </p>
<p>EDIT: also if a=b then they are both 45. therefore k is 45 and c=k. those both can’t be correct either. So the only possible choice is d.</p>
<p>a+b+90 = 180 so a+b=90. also, b+c=90 and c+k=90.</p>
<p>subtract pairs to get a=c or b=k. or, you could see that by reasoning that the lines that make, say, angles a and c have to be parallel since the squares have to tilt the same way (they’re touching, after all). </p>
<p>don’t think b and c are equal just because of the diagram. the squares could actually be tilted to, say, the left, making b larger.</p>